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/pubsub.js

@@ -0,0 +1,50 @@
+// 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/>.
+
+import Eth from './eth';
+import Parity from './parity';
+import Net from './net';
+
+import { isFunction } from '../util/types';
+
+export default class Pubsub {
+  constructor (transport) {
+    if (!transport || !isFunction(transport.subscribe)) {
+      throw new Error('Pubsub API needs transport with subscribe() function defined. (WebSocket)');
+    }
+
+    this._eth = new Eth(transport);
+    this._net = new Net(transport);
+    this._parity = new Parity(transport);
+  }
+
+  get net () {
+    return this._net;
+  }
+
+  get eth () {
+    return this._eth;
+  }
+
+  get parity () {
+    return this._parity;
+  }
+
+  unsubscribe (subscriptionIds) {
+    // subscriptions are namespace independent. Thus we can simply removeListener from any.
+    return this._parity.removeListener(subscriptionIds);
+  }
+}