PubSub for parity-js (#5830)

* PubSub Integration WebSocket

* PubSub Provider API

* Parity License and fix switch statement

* Minor fix: use parameter api

* Exclude subscriptionId return

* Unsubscribe parameters as array

* secureProvider API added

* isSecure check

* Refractor: Formatting in callback (no Promise)

* Tests for parityProvider

* Refractor: Formatting in callback (secure API)

* Updated transaction documentation

* Module instead of API-Names, Options always as array (e.g. empty)

'parity' instead of 'parity_subscribe' calls
params with empty array as options. If eth_subscribe includes empty array parity-core will send invalid request (eth api doesn't have options)

* Removed isSecure transport check, because APIs are configurable

* Refractor Provider API to single Pubsub

* Modify transport layer to have single identifier for subscriptions

* FIX: Display pubsub errors

* Discard Messages after unsubscribing

* Fix: display error normal messages correctly

* Simplified code, removed unnecessary pubsub methods

* trace_call API 2nd argument blockNumber, first whatTrace

https://github.com/paritytech/parity/wiki/JSONRPC-trace-module#trace_call

* Separate namespaces pubsub. eth, parity, net

* Keep error for messages from unsubscribed topics.

* Fix: Unsubscribe Promise

* Add Test: Unsubscribe promise resolved

* Fix: 'error' in params

js/src/api/pubsub/pubsubBase.js

@@ -0,0 +1,37 @@
+// Copyright 2015-2017 Parity Technologies (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+export default class PubsubBase {
+  // Provider for websocket pubsub transport
+  constructor (transport) {
+    this._transport = transport;
+  }
+
+  addListener (module, eventName, callback, eventParams) {
+    return eventParams
+     ? this._transport.subscribe(module, callback, eventName, eventParams)
+     : this._transport.subscribe(module, callback, eventName, []);
+    // this._transport.subscribe(module, callback, eventName);  After Patch from tomac is merged to master! =>  eth_subscribe does not support empty array as params
+  }
+
+  removeListener (subscriptionIds) {
+    return this._transport.unsubscribe(subscriptionIds);
+  }
+
+  unsubscribe (subscriptionIds) {
+    return this.removeListener(subscriptionIds);
+  }
+}