- If a header was marked as checked before a transformer was added to
the watcher, mark all headers since the new transformer's starting
block number as unchecked.
- limit missing headers results set to 100 so that extraction doesn't
excessively block delegation
- wrap checked headers functions in repository struct
- move storage repository to factory, to correspond with event
repository path
- remove unused files
- reformat sql
- remove line breaks in imports