Implement EIP234 block_hash for eth_getLogs (#9256)

* Implement EIP234

* Make filter conversion returns error if both blockHash and from/toBlock is found

This also changes PollFilter to store the EthFilter type, instead of the jsonrpc one, saving repeated conversion.

* Return error if block filtering target is not found in eth_getLogs

Use the old behavior (unwrap_or_default) for anywhere else.

* fix test: secret_store

* Fix weird indentation

* Make client log filter return error in case a block cannot be found

* Return blockId error in rpc

* test_client: allow return error on logs

* Add a mocked test for eth_getLogs error

* fix: should return error if from_block/to_block greater than best block number

* Add notes on pending

* Add comment for UNSUPPORTED_REQUEST

* Address grumbles

* Return err if from > to

ethcore/src/tests/client.rs

@@ -150,7 +150,7 @@ fn returns_logs() {
 		address: None,
 		topics: vec![],
 		limit: None,
-	});
+	}).unwrap();
 	assert_eq!(logs.len(), 0);
 }
 
@@ -164,7 +164,7 @@ fn returns_logs_with_limit() {
 		address: None,
 		topics: vec![],
 		limit: None,
-	});
+	}).unwrap();
 	assert_eq!(logs.len(), 0);
 }