* ssz: update to 0.5.1:ish
* slightly fewer seq allocations
* still a lot of potential for optimization
* fixes#174
* ssz: avoid reallocating leaves (logN merkle impl)
* update processExits to 0.5.1
* mark process_deposit, get_empty_block as 0.5.1; update get_genesis_beacon_state to 0.5.1; implement processDeposits
* hotfix via https://github.com/ethereum/eth2.0-specs/pull/821
* rm gone-in-0.5.0 Proposal, verifyBlockSignature, and slot check which moved to spec function processBlockHeader
* mark get_attestation_participants and get_epoch_committee_count as 0.5.1; finish updating processAttestations to 0.5.1; add kludgy workaround for bug relating to get_winning_roots_etc using crosslink_data_root as index when we have that as ZERO_HASH for all leading to it confusing attesters on different shards; rm BeaconState.latest_attestations, which splits into previous_epoch_attestations and current_epoch_attestations
* Fix CI due to removed latest_attestations field
* 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
* begin refactoring 0.5.0 epoch transition at justification and finalization
* update processTransfers to 0.5.0 spec
* update get_crosslink_committees_at_slot to 0.5.0 except for noted workaround for pre-0.5.0 spec bug related to epoch boundary conditions, to be flipped in more coordinated way with other epoch processing changes
* mark ejection processing as 0.5.0
* 0.5.0 epoch update finalization
* rm BEACON_CHAIN_SHARD_NUMBER to complete updating miscellaneous constants to 0.5.0
* mark verify_slashable_attestation as 0.5.0
* update process_attester_slashing to 0.5.0
* update process_slashings(...) to 0.5.0 and mark process_exit_queue as 0.5.0
* refactor epoch processing by implementing 0.5.0's update_registry_and_shuffling_data(...)
With these changes, running a simulation is very close to running
an actual testnet. Some checks have been added in the client to
make sure you are not connecting to an incompatible network (e.g.
a network running with a different number of shards).
* begin 0.5.0 spec update: parent_root -> previous_block_root, BeaconState.justified_epoch -> BeaconState.current_justified_epoch, DOMAIN_PROPOSAL -> DOMAIN_BEACON_BLOCK, temporarily rename BeaconBlockHeader to BeaconBlockHeaderRLP to allow for gradual re-merging without disrupting RLP; mark a few unchanged functions and data types, implement get_temporary_block_header/get_empty_block/should_update_validator_registry/processBlockHeader/cacheState; update a few others
* a dozen or so more trivial mostly comment changes, finding more unchanged parts of 0.5.0
* several more trivial changes; goal is to reduce noise around the upcoming substantial changes (epoch processing, etc)
* remove some redundant state updates
* when attesting late, use correct state / head
* don't send out obsolete attestations
* don't propose obsolete blocks
* remove some more resundant state updates :)
* simplify block logging (experimental)
* document fork choice division
* fix some Slot / Epoch conversion warnings
* 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)
Passing along no-name command line arguments when using make (from Nimbus) would need make target revamps that are a bit clumsy AFAIK, so using environment variables in the spirit of USE_MULTITAIL to get the number of validators and nodes makes more sense to me.
This lets us run the sim from nim-beacon-chain with
```bash
VALIDATORS=512 NODES=100 USE_MULTITAIL="yes" tests/simulation/start.sh
```
and from Nimbus with:
```bash
VALIDATORS=512 NODES=100 USE_MULTITAIL="yes" make eth2_network_simulation
```
Also makes for a more verbose launch process.
Zahary Karadjov
Jacek Sieka
Bruno Škvorc
Dustin Brody
Jacek Sieka
Mamy André-Ratsimbazafy
Yuriy Glukhov
Ștefan Talpalaru
Andrea Franz