* relax attestation validation when attestation is incoming but make it
more strict when adding to block
* share attestation validation logic between attestation pool and state
transition
* remove a bunch of redundant logging
* fix potential underflow in attestation delay checking
* fix committee used for attestation shard selection when attesting
* fix attestation data construction
* working justification, 1 node, 64 validators
* closer to tn1 params: 256 validators
* more debugging output; switch to minimum test case
* working justification and finalization in local network simulation
* fix currently incorrect state transition/attestation test assumption
* replace BeaconState.finalized_{epoch,root} with BeaconState.finalized_checkpoint; rename get_delayed_activation_exit_epoch(...) to compute_activation_exit_epoch(...) and mark as 0.8.0; update get_churn_limit(...)/get_validator_churn_limit(...) to 0.8.0; update process_registry_updates(...) to 0.8.0
* update process_crosslinks(...) to 0.8.0; mark compute_start_slot_of_epoch(...) and get_committee_count(...) as 0.8.0
* mark Fork, is_slashable_validator(...), and get_beacon_proposer_index(...) as 0.8.0
* rename LATEST_SLASHED_EXIT_LENGTH to EPOCHS_PER_SLASHINGS_VECTOR; update process_slashings(...) to 0.8.0; remove pointless type conversion warning in get_previous_epoch(...)
* convert remaining references to finalized_epoch to finalized_checkpoint.epoch
* update slash_validator(...) to 0.8.0; mark inital value, Gwei, and time constants as 0.8.0; mark hash(...) and processBlockHeader(...) as 0.8.0
* rename WHISTLEBLOWING_REWARD_QUOTIENT to WHISTLEBLOWER_REWARD_QUOTIENT; rename LATEST_ACTIVE_INDEX_ROOTS_LENGTH to EPOCHS_PER_HISTORICAL_VECTOR (randao will also get merged into this); remove get_active_index_root(...); mark time parameter, signature domain types, and max operations per block constants as 0.8.0; update rewards and penalties constants to 0.8.0
* update is_valid_indexed_attestation(...) to 0.8.0; mark process_slot(...) as 0.8.0
* replace BeaconState.{current,previous}_justified_{epoch,root} with BeaconState.{current,previous}_justified_checkpoint
* rename slot_to_epoch(...) to compute_epoch_of_slot(...)
* rename aggregation_bitfield/custody_bitfield fields to aggregation_bits/custody_bits; rename convert_to_indexed(...) to get_indexed_attestation(...); mark BeaconBlockHeader as 0.8.0; update minimal preset MIN_ATTESTATION_INCLUSION_DELAY/time parameters in general to 0.8
* fix beacon node compilation; it used slightly different capitalizations of slot_to_epoch/slotToEpoch
* mark integer_squareroot(...), Deposit, VoluntaryExit, and Transfer as 0.8.0; rename get_epoch_start_slot(...) to compute_start_slot_of_epoch(...)
* add new Domain alias for uint64; rename bls_domain(...) to compute_domain(...), MAX_INDICES_PER_ATTESTATION to MAX_VALIDATORS_PER_COMMITTEE, and SignatureDomain to DomainType; update get_domain(...) to 0.8.0
* update/mark initiate_validator_exit(...) and Crosslink as 0.8.0; rename BeaconState.latest_block_roots -> BeaconState.block_roots; mark HistoricalBatch as 0.8.0
* migrate attestation pool tests from get_crosslink_committees_at_slot(...) to get_crosslink_committee(...)
* rm obsolete, unused get_crosslink_committees_at_slot_cached(...) and migrate tests/test_state_transition from get_crosslink_committees_at_slot(...) to get_crosslink_committee(...)
* migrate tests/testutil from get_crosslink_committees_at_slot(...) to get_crosslink_committee(...)
* use more pervasive caching infrastructure, initially of compute_committee; remove buggy (and per-index) shuffling to fix research/state_sim, which was noticing validators on multiple shard committees; rm now-unused specific get_attesting_balance_cached
* add some get_active_validator_index caching
* rm obsolete/unused get_attesting_indices_cached
* rm get_crosslink_committees_at_slot(...)
* some more 0.7 changes -- some of which can't be completed pending some data structure updates -- and shard handling changes to offset with epoch start shards
* update IndexedAttestation, verify_slashable_attestation/verify_indexed_attestation, and attester slashing processing to 0.6.3
* rm debug scaffolding
* rename Attestation.aggregate_signature -> Attestation.signature; convert various references to AttestationData.slot to get_attestation_slot; implement convert_to_indexed; update checkAttestation and processAttestations to 0.6.3; remove spurious assertion in beacon node related to invalid attestations
* replace 0.5 get_winning_root_and_participants with 0.6 get_winning_crosslink_and_attesting_indices; update process_crosslinks to 0.6.3
* mark both remaining 0.6.0 spec implementations as 0.6.3
* clear out all remaining spec version 0.6.1 refs
* GENESIS_SLOT and GENESIS_EPOCH are 0
* rm 0.5 get_attestation_participants in favor of 0.6 get_attesting_indices
* address mratsim's comment
* time can be equal to genesis
* fix invalid block assertions; those were essentially spurious
* allow toBeaconTime to handle time before genesis (in accordance with now(...) which states time can exist before GENESIS)
* begin 0.6.0: new get_domain/increase_balance/reduce_balance, BeaconState.validator_balances -> BeaconState.balances, some renamed constants, transaction processing changes, SlashableAttestation field name changes, 0.6.0 get_beacon_proposer_index always uses given state's slot, update tests subrepo
* mark get_bitfield_bit/bls_verify_multiple/stat-list-lengths/is_active_validator/is_surround_vote/slot_to_epoch/int_to_bytes/etc as unchanged in 0.6.0; rm Eth1DataVote/maybe_reset_eth1_period and thus adjust expected tree hash test results
* mark verify_bitfield/bls_verify/deposit-contract/VoluntaryExit/PendingAttestation/Historicalbatch/Fork as 0.6.0; update DOMAIN_BEACON_BLOCK to DOMAIN_BEACON_PROPOSER
* update Crosslink to 0.6.0 (also requires tree hashing test result change, so isolate in individual commit)
* mark verify_merkle_branch/get_delayed_activation_exit_epoch/ProposerSlashing/Attestation/AttestationDataAndCustodyBit/hash/integer_squareroot/get_epoch_start_slot/is_double_vote/get_randao_mix/generate_seed as 0.6.0; update reward and penalty quotients; SlashableAttestation -> IndexedAttestation; rm get_fork_version; ATTESTATION_INCLUSION_REWARD_QUOTIENT -> PROPOSER_REWARD_QUOTIENT
* have regular slot tick, decide on work to do lazily
* use beacon clock instance that will eventually sync time
* skip work when falling behind
* add one more state cache for justified state (since that's used in
fork choice)
* remove old sync cruft
* single timer per slot, serializing block production and attestation
* add simple bitfield type (fixes#19)
* fix bit endianess to match spec
* consolidate attestation and block logging
* cruft cleanup
* run optimizer on tests, speeds up build
* keep track of a finalized block
* keep track of all justified blocks
* use naive spec version of LMD ghost
* cache slot number and a few more things in BlockRef
* keep track of the latest vote of each validator
* depend less on the state of node.state (it's a cache, effectively)
* implement in-memory block graph
* store tail block in database
* resolve unknown parents by syncing them from peers
* introduce concept of resolved blocks and attestations - those that
follow minimal protocol rules
* update state head lazily
* log more stuff
* shortHash -> shortLog
* start 9/10 beacon nodes by default, last can be started manually
* see also #134
* fix start.sh epoch length
* fix initial attestation pool on reordered attestations
* simplify db layer api
* load head block from database on startup, then load state
* significantly changes database format
* move subscriptions to separate proc's
* implement block replay from historical state
* avoid rescheduling epoch actions on block receipt (why?)
* make sure genesis block is created and used
* relax initial state sim parameters a bit
* move attestation pool to separate file
* combine attestations lazily when needed
* advance state when there's a gap while attesting
* compile beacon node with optimizations - it's tooo slow right now
* log when unable to keep up