* beacon: draft update of definition to v0.9.0

* beacon: (typo) clone eth1_data.block_hash

* Pass all minimal tests

* Fix validator implementation

* beacon: fix mainnet config min_attestation_inclusion_delay

Merge interop work branch back to master

It's not needed because things are not stored in lfs any more!

docs: add security policy

Future-based syncing module

It's outdated and the interface has vastly changed. Removed temporarily to add
it back later.