- kvdb
	- Fix path in Last when doing `setNew`
	- Only close if db != nil, and after closing, always set db to nil
		- This will avoid a panic in the case where the db is closed but
		  there's an error soon after, and a future call tries to close
		  again.  This is because pebble.Close() will panic if the db is
		  already closed.
	- Avoid calling pebble methods when a the Storage interface already
	  implements that method (like Close).
- statedb
	- In test, avoid calling KVDB method if the same method is available for
	  the StateDB (like MakeCheckpoint, CurrentBatch).
- eth
	- In *EventByBlock methods, take blockHash as input argument and use it
	  when querying the event logs.  Previously the blockHash was only taken
	  from the logs results *only if* there was any log.  This caused the
	  following issue: if there was no logs, it was not possible to know if
	  the result was from the expected block or an uncle block!  By querying
	  logs by blockHash we make sure that even if there are no logs, they
	  are from the right block.
	  	- Note that now the function can either be called with a
		  blockNum or blockHash, but not both at the same time.
- sync
	- If there's an error during call to Sync call resetState, which
	  internally resets the stateDB to avoid stale checkpoints (and a
	  corresponding invalid increase in the StateDB batchNum).
	- During a Sync, after very batch processed, make sure that the StateDB
	  currentBatch corresponds to the batchNum in the smart contract
	  log/event.