Provider testing improvements

New: Test button for indexers in UI

Fixed: Testing download clients shows error messages in UI
Fixed: Testing notifications shows error messages in UI

src/UI/Settings/Notifications/NotificationModel.js

@@ -1,10 +1,9 @@
 'use strict';
-define([
-    'Settings/SettingsModelBase'
-], function (ModelBase) {
-    return ModelBase.extend({
 
-        successMessage: 'Notification Saved',
-        errorMessage  : 'Couldn\'t save notification'
+define([
+    'Settings/ProviderSettingsModelBase'
+], function (ProviderSettingsModelBase) {
+    return ProviderSettingsModelBase.extend({
+
     });
 });