* Log checked headers for Bite events
* Log checked headers for Drip drip events
* Log checked headers for Drip file events
- mark headers checked for 3 implementations of file on the Drip contract
* Log checked headers for Frob frob events
* Log checked headers for Pit file events
- mark headers checked for 3 implementations of file on the Pit contract
* Log checked headers for Vat init events
- Enables parsing additional values off the log if necessary
- Also update Frob to reflect DSS changes (lad => urn)
- Move Frob constants to shared directory
- fetches logs from all three price feeds in one query
- assumes eth/usd price feed will be updated to include LogValue event
- updates transformers to run separate from header sync
