Incorrect block author

[hseeberger]

The indexer fetches the authorities, which are used to determine the block author, for the latest block. While this would possibly work well when the Indexer has caught up, it could result in incorrect block authors for "old" blocks that are being indexed.

[hseeberger]

This should be fixed by #318. Keeping it open until we can test/verify it.
//cc @GiuseppeSalvatoreShielded