Remove all code referencing old tab navigation

Summary:
  - Add getHelpURI() to PhabricatorApplication for application user guides.
  - Add a new "help" icon menu item and skeletal Diviner application.
  - Move help tabs to Applications where they exist, document the other ones that don't exist yet.
  - Grep for all tab-related stuff and delete it.

Test Plan: Clicked "help" for some apps. Clicked around randomly in a bunch of other apps.

Reviewers: btrahan, vrana

Reviewed By: btrahan

CC: aran

Differential Revision: https://secure.phabricator.com/D3267

src/applications/phriction/controller/PhrictionController.php

@@ -30,14 +30,6 @@ abstract class PhrictionController extends PhabricatorController {
     $page->setTitle(idx($data, 'title'));
     $page->setGlyph("\xE2\x9A\xA1");
 
-    $tabs = array(
-      'help' => array(
-        'name' => 'Help',
-        'href' =>
-          PhabricatorEnv::getDoclink('article/Phriction_User_Guide.html'),
-      ),
-    );
-    $page->setTabs($tabs, idx($data, 'tab'));
     $page->appendChild($view);
     $page->setSearchDefaultScope(PhabricatorSearchScope::SCOPE_WIKI);