* collect signature production and verificaiton in one place
Signatures are made over data and domain - here we collect all such
activities in one place.
Also:
* security: fix cast-before-range-check
* log block/attestation verification consistently
* run block verification based on `getProposer` in its own history
* clean up some unused stuff
* import
* missing raises
* reorder ssz
* split into hash_trees and ssz_serialization, roughly, for hashing and
IO
* move bitseqs into ssz (from stew)
* clean up imports
* docs, imports
* crypto: cleanup
* fix several Defect-on-user-input
* make crypto interface more similar to secp
* use `crypto.nim` in all of nbc
* digest: raises
* fix
* vendor
* refactor and fix merkle proof construction in test suite and thereby remove most remaining skipMerkleValidation flags, now unnecessary
* a few non-semantic comment update/removals
* initial attestation aggregation
* fix usage of committee index, vs index in committee; uniformly set trailing/following distance; document how the only-broadcast-if mechanism works better and what aggregation already happens, not otherwise sufficiently clear; use correct BlockSlot across epoch boundaries
* address inconsistent notion of which slot in past to target for aggregate broadcast; follow 0.11.x aggregate broadcast p2p interface topic
* Fix get_slot_signature(...) call after get_domain(...) change required genesis_validators_root
* mark all spec references which aren't dealt with in other PRs as v0.11.1
* update two more spec refs to v0.11.1
* initial extended validation setup
* flesh out all TODO items for attestation and beaconblock verification
* fix finalization and add chronicles debugging messages
* directly use blockPool.headState rather than pointlessly updating it and document this constraint
* fix logic relating to first-attestation checking; support validating blocks across multiple forks
Dustin Brody
Eugene Kabanov
Jacek Sieka
Mamy Ratsimbazafy