* fix subnet calculation in RPC and insert broadcast attestations into node's pool
* unify codepaths to ensure only mostly-checked-to-be-valid attestations enter the pool, even from node's own broadcasts
* update attestation pool tests for new validateAttestation param
* make subnet cycling more robust; use one stability subnet/validator; explicitly represent gossip enabled/disabled
* fix asymmetry in _snappy being used for subscriptions but not unsubscriptions
* remove redundant comment
* minimal RPC and VC support for infoming BN of subnets
* create and verify slot signatures in RPC interface and VC
* loosen old slot check
* because Slot + uint64 works but uint64 + Slot doesn't
* document assumptions for head state use; don't clear stability subnets; guard against VC not having checked an epoch ahead, fixing a crash; clarify unsigned comparison
* revert unsub fix
tersec
Eugene Kabanov
Jacek Sieka
Zahary Karadjov