Add a meta-application

Summary:
  - Adds a new "Applications" application.
  - Builds an application list via application config instead of via hard-coding, so we can move toward better concepts of installing/uninstalling applications, etc.
  - Applications indicate that they need attention with notice counts and brief status messages rathern than 50 giant tables of all sorts of app data.

I want to try replacing the home screen with this screen, pretty much. Not sure if this is totally crazy or not. What does everyone else think?

Test Plan: Will add screenshots.

Reviewers: btrahan, chad, vrana, alanh

Reviewed By: vrana

CC: aran, davidreuss, champo

Maniphest Tasks: T1569

Differential Revision: https://secure.phabricator.com/D3129

src/applications/diffusion/application/PhabricatorApplicationDiffusion.php

@@ -0,0 +1,34 @@
+<?php
+
+/*
+ * Copyright 2012 Facebook, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+final class PhabricatorApplicationDiffusion extends PhabricatorApplication {
+
+  public function getShortDescription() {
+    return 'Repository Browser';
+  }
+
+  public function getBaseURI() {
+    return '/diffusion/';
+  }
+
+  public function getIconURI() {
+    return celerity_get_resource_uri('/rsrc/image/app/app_diffusion.png');
+  }
+
+}
+