Provide wallet 'plugin' architecture (#1983)

* remove receive_coinbase fn from wallet to wallet client

* start moving clients into separate mod

* rustfmt

* move wallet client + start listener into wallet 'clients'

* rustfmt

* refactor API to make it more modular and completely decouple sending

* rustfmt

* further decouple API from sending methods

* rustfmt

* remove wallet to wallet client trait

* rustfmt

* rename / refactor client + adapters

* rustfmt

* add adapter concept

* add midding node_clients dir

* add file and null adapters

* rustfmt

* remove receive from owner api

* factor out receiving slates into trait

* rustfmt

* adding listen trait

* rustfmt

* change listener to use trait

* rustfmt

* add test for file-based exchange

* replace http api send command

* rustfmt

* move controller out of libwallet and into top-level wallet dir

* rustfmt

* add moved controller

api/src/rest.rs

@@ -92,8 +92,8 @@ impl From<Context<ErrorKind>> for Error {
 
 /// TLS config
 pub struct TLSConfig {
-	certificate: String,
-	private_key: String,
+	pub certificate: String,
+	pub private_key: String,
 }
 
 impl TLSConfig {
@@ -190,7 +190,7 @@ impl ApiServer {
 			.spawn(move || {
 				let server = Server::bind(&addr)
 					.serve(router)
-					// TODO graceful shutdown is unstable, investigate 
+					// TODO graceful shutdown is unstable, investigate
 					//.with_graceful_shutdown(rx)
 					.map_err(|e| eprintln!("HTTP API server error: {}", e));