* Add attestation unit test
* process_attestation doesn't throw exceptions
* Allow SSZ deserialization of both real and invalid signatures
* Add new process_attestation checks - pass all process_attestation tests
* Add sanity check for #361
* Fix SSZ testing after fromBytes/fromSSZBytes changes
* Add sanity check for slot processing (also impacted by https://github.com/status-im/nim-beacon-chain/issues/373)
* use reportDiff also for all state tests vs EF
* initial sanity checks for blocks - workaround zero signature in block headers: https://github.com/status-im/nim-beacon-chain/issues/374
* Remove generic object variant compare commented code
* Add the one block state transition sanity checks
* generalize blocks test to multiple blocks
* simplify slots test runner
* Add official epoch transitions, sanity blocks, sanity slots to the test suite
* Fix index out-of-bounds in initiate_validator_exit - enable proposer slashings unittest