* 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 Deposit and BeaconBlockHeader to 0.7.0
* update get_total_balance(...) and get_base_reward(...) to 0.7.0
* rename initial value constant BLS_WITHDRAWAL_PREFIX_BYTE to BLS_WITHDRAWAL_PREFIX
* mark minimal presets as entirely migrated to 0.7.0; update process_rewards_and_penalties(...) to 0.7.0
* specify that targeting 0.7.0; adopt 0.7.0 refactoring of bls_domain/get_domain to update get_domain(...) to 0.7.0; mark that mainnet constant presets and block header processing are 0.7.0-consistent; update process_justification_and_finalization to 0.7.0 to fix potential underflow errors
* address mratsim's comment to copy whole spec comment
* 0.7.0 updates which don't change semantics; mostly comment changes
* mark get_attesting_indices, bls_verify, ProposerSlashing, BeaconBlockBody, deposit contract constants, state list length constants, compute_committee, get_crosslink_committee, is_slashable_attestation_data, processAttesterSlashings as 0.7.0; rename BASE_REWARD_QUOTIENT to BASE_REWARD_FACTOR
* complete marking unchanged-in-0.7.0 datatypes as such; a few more have trivial field renamings, etc
* 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)
* Proto changes to facilitate backward sync
* Update to latest spec types in sync proto
* Use blockpool for more straightforward block headers collection
* Added BlockPool.getRef
* Update beacon_chain/sync_protocol.nim
Co-Authored-By: Jacek Sieka <arnetheduck@gmail.com>