- Delete header on conflict to prompt data refresh (cascade deletes all
data associated with that block)
- Derive header hash from rpc payload rather than computing it from data
(prevents hash mismatch between blockchain and cache)
* Add log_index field to flip kick
* Add log index to flop kick
* Add repo tests for Cat.file
* Add log_index to vat_flux
* Add log_index to vat_slip
* Add log_index to vat_toll
* Add log_index to vat_tune
* Add test to repos for updating checked headers
