Use ethcore_dappsPort when constructing URLs (#3139)

* Upon connect, retrieve the available api ports

* Update dapps to load from dappsPort

* Update dapps summary with dappsPort

* Allow proxy to use dappsPort

* Replace /api/ping with HEAD /

* Dynamic port for available apps

* Retrieve content images with dappsPort

* Fix /

* Transfer token dropdown image fix

* IdentityIcon loads images via contentHash

* Update apps fetch to cater for dev & prod

* DRY up 127.0.0.1:${dappsPort} with ${dappsUrl}

js/src/redux/providers/imagesReducer.js

@@ -17,8 +17,6 @@
 import { handleActions } from 'redux-actions';
 import { bytesToHex } from '../../api/util/format';
 
-import { parityNode } from '../../environment';
-
 const ZERO = '0x0000000000000000000000000000000000000000000000000000000000000000';
 
 const initialState = {
@@ -28,7 +26,7 @@ const initialState = {
 export function hashToImageUrl (hashArray) {
   const hash = hashArray ? bytesToHex(hashArray) : ZERO;
 
-  return hash === ZERO ? null : `${parityNode}/api/content/${hash.substr(2)}`;
+  return hash === ZERO ? null : `/api/content/${hash.substr(2)}`;
 }
 
 export default handleActions({

js/src/redux/providers/status.js

@@ -16,8 +16,6 @@
 
 import { statusBlockNumber, statusCollection, statusLogs } from './statusActions';
 
-import { parityNode } from '../../environment';
-
 export default class Status {
   constructor (store, api) {
     this._api = api;
@@ -65,7 +63,7 @@ export default class Status {
       setTimeout(this._pollPing, timeout);
     };
 
-    fetch(`${parityNode}/api/ping`, { method: 'GET' })
+    fetch('/', { method: 'HEAD' })
       .then((response) => dispatch(!!response.ok))
       .catch(() => dispatch(false));
   }