* plumbing between block pool and state transition functions around active validator indices and committees
* have shared epochrefs followed by blockref tree while allowing for skipped slots
* factor out the epoch info extraction; document how the EpochRef follows forks
* in makeBeaconBlock - use rollback instead
* in tests - this helps state_sim give more accurate data and makes it
30% faster
* fix some usages of raw BeaconState
tersec
Jacek Sieka
Mamy Ratsimbazafy