RPC: parity_getBlockReceipts (#9527)

* Block receipts RPC.

* Use lazy evaluation of block receipts (ecrecover).

* Optimize transaction_receipt to prevent performance regression.

* Fix RPC grumbles.

* Add block & transaction receipt tests.

* Fix conversion to block id.

ethcore/light/src/provider.rs

@@ -176,7 +176,7 @@ impl<T: ProvingBlockChainClient + ?Sized> Provider for T {
 	}
 
 	fn block_receipts(&self, req: request::CompleteReceiptsRequest) -> Option<request::ReceiptsResponse> {
-		BlockChainClient::block_receipts(self, &req.hash)
+		BlockChainClient::encoded_block_receipts(self, &req.hash)
 			.map(|x| ::request::ReceiptsResponse { receipts: ::rlp::decode_list(&x) })
 	}