Changed how logs are being recorded

Logs are now recorded per transactions instead of tossing them out after
each transaction. This should also fix an issue with
`eth_getFilterLogs` (#629) Also now implemented are the `transactionHash,
blockHash, transactionIndex, logIndex` on logs. Closes #654.

core/vm/environment.go

@@ -22,7 +22,7 @@ type Environment interface {
 	Difficulty() *big.Int
 	GasLimit() *big.Int
 	Transfer(from, to Account, amount *big.Int) error
-	AddLog(state.Log)
+	AddLog(*state.Log)
 
 	VmType() Type