Asynchronous RPC support (#2017)

* Async RPC

* Limiting number of transactions in queue

* Fixing tests

* Bumping serde and jsonrpc-core

* serde updated to 0.8

* fixed failing tests

* Bumping ipc server

* Fixing API for endpoints

* Experimenting with tests without --release mode

dapps/src/endpoint.rs

@@ -16,7 +16,7 @@
 
 //! URL Endpoint traits
 
-use hyper::{server, net};
+use hyper::{self, server, net};
 use std::collections::BTreeMap;
 
 #[derive(Debug, PartialEq, Default, Clone)]
@@ -43,4 +43,8 @@ pub trait Endpoint : Send + Sync {
 	fn info(&self) -> Option<&EndpointInfo> { None }
 
 	fn to_handler(&self, path: EndpointPath) -> Box<Handler>;
+
+	fn to_async_handler(&self, path: EndpointPath, _control: hyper::Control) -> Box<Handler> {
+		self.to_handler(path)
+	}
 }