* panic in SizeSSZ
* moving slowly
* adapt old code to new interfaces
* return interfaces from factory functions
* replace the rest of WrappedSignedBeaconBlock
* WrappedBeaconBlock
* WrappedBeaconBlockBody
* miscellaneous
* Test_BeaconBlockIsNil
* replace usages of BeaconBlockIsNil
* replace usages of mutator
* fix all build errors
* fix some more issues
* mutator changes
* relax assertions when initializing
* revert changes in object_mapping.go
* allow calling Proto on nil
* Revert "allow calling Proto on nil"
This reverts commit ecc84e455381b03d24aec2fa0fa17bddbec71705.
* modify Copy and Proto methods
* remove unused var
* fix block batch tests
* correct BUILD file
* Error when initializing nil objects
* one more error fix
* add missing comma
* rename alias to blocktest
* add logging
* error when SignedBeaconBlock is nil
* fix last test
* import fix
* broken
* working
* test fixes
* reduce complexity of processPendingBlocks
* simplified
* Move domain function and all signing root functions from beacon-chain/core/helpers to beacon-chain/core
* @terencechain suggestion to put these methods under core/signing
