Fix filter_block_not_found error message

[sorpaas]

Address grumble #9256 (review)
cc @jimpo

[ordian]

I would prefer having a separate message for that error, something like that:

pub fn filter_block_error(id: BlockId, msg: &str) -> Error {
	Error {
		code: ErrorCode::ServerError(codes::UNSUPPORTED_REQUEST), // Specified in EIP-234.
		message: msg.into(),
		data: Some(Value::String(match id {
			BlockId::Hash(hash) => format!("0x{:x}", hash),
			BlockId::Number(number) => format!("0x{:x}", number),
			BlockId::Earliest => "earliest".to_string(),
			BlockId::Latest => "latest".to_string(),
		})),
	}
}
pub fn filter_block_not_found(id: BlockId) -> Error {
	filter_block_error(id, "One of ...")
}
pub fn filter_block_out_of_order(id: BlockId) -> Error {
	filter_block_error(id, "fromBlock and toBlock are out of order")
}

[sorpaas]

I think this needs a custom error type in ethcore, and we cannot use ? syntax any more for the Client::logs function. Not sure it would worth it or not, but let me give a try.

[sorpaas]

I think this would indeed need some amounts of change in Client error types, or we would need to duplicate the checks in Client::logs in RPC again (which I don't think is a good idea). For the former, I think it may be better to fix this together with a Client and Blockchain struct error type overhaul, so that we can preserve using ? syntax there. So I'm going to temporarily close this.

I created an issue #9373.