Big front-end asset/filestructure refactor

- Extract shared Ember components into a “flarum-common” ember-cli
addon. This can be used by both the forum + admin Ember apps, keeping
things DRY
- Move LESS styles into their own top-level directory and do a similar
thing (extract common styles)
- Add LESS/JS compilation and versioning to PHP (AssetManager)
- Set up admin entry point

(Theoretical) upgrade instructions:
- Delete everything in [app_root]/public
- Set up tooling in forum/admin Ember apps (npm install/update, bower
install/update) and then build them (ember build)
- php artisan vendor:publish
- Upgrade flarum/flarum repo (slight change in a config file)
- If you need to trigger a LESS/JS recompile, delete the .css/.js files
in [app_root]/public/flarum. I set up LiveReload to do this for me when
I change files in less/ or ember/

Todo:
- Start writing admin app!
- Remove bootstrap/font-awesome from repo and instead depend on their
composer packages? Maybe? (Bower is not an option here)

src/Admin/Actions/IndexAction.php

@@ -0,0 +1,54 @@
+<?php namespace Flarum\Admin\Actions;
+
+use Flarum\Web\Actions\Action;
+use Illuminate\Http\Request;
+use Session;
+use Auth;
+use Cookie;
+use Config;
+use View;
+
+class IndexAction extends Action
+{
+    public function handle(Request $request, $params = [])
+    {
+        $config = [
+            'modulePrefix' => 'flarum-admin',
+            'environment' => 'production',
+            'baseURL' => '/admin',
+            'apiURL' => '/api',
+            'locationType' => 'hash',
+            'EmberENV' => [],
+            'APP' => [],
+            'forumTitle' => Config::get('flarum::forum_title', 'Flarum Demo Forum')
+        ];
+        $data = [];
+        $session = [];
+        $alert = Session::get('alert');
+
+        if (($user = $this->actor->getUser()) && $user->exists) {
+            $session = [
+                'userId' => $user->id,
+                'token' => Cookie::get('flarum_remember')
+            ];
+
+            $response = $this->callAction('Flarum\Api\Actions\Users\ShowAction', ['id' => $user->id]);
+            $response = $response->getData();
+
+            $data = [$response->data];
+            if (isset($response->included)) {
+                $data = array_merge($data, $response->included);
+            }
+        }
+
+        return View::make('flarum.admin::index')
+            ->with('title', Config::get('flarum::forum_title', 'Flarum Demo Forum'))
+            ->with('styles', app('flarum.admin.assetManager')->getCSSFiles())
+            ->with('scripts', app('flarum.admin.assetManager')->getJSFiles())
+            ->with('config', $config)
+            ->with('content', '')
+            ->with('data', $data)
+            ->with('session', $session)
+            ->with('alert', $alert);
+    }
+}

src/Admin/AdminServiceProvider.php

@@ -0,0 +1,45 @@
+<?php namespace Flarum\Admin;
+
+use Illuminate\Support\ServiceProvider;
+use Flarum\Web\AssetManager;
+
+class AdminServiceProvider extends ServiceProvider
+{
+    /**
+     * Bootstrap the application events.
+     *
+     * @return void
+     */
+    public function boot()
+    {
+        $root = __DIR__.'/../..';
+
+        $this->loadViewsFrom($root.'/views', 'flarum.admin');
+
+        $assetManager = $this->app['flarum.admin.assetManager'];
+
+        $assetManager->addFile([
+            $root.'/ember/admin/dist/assets/vendor.js',
+            $root.'/ember/admin/dist/assets/flarum-admin.js',
+            $root.'/less/admin/app.less'
+        ]);
+
+        $this->publishes([
+            $root.'/public/fonts' => public_path('flarum/fonts')
+        ]);
+
+        include __DIR__.'/routes.php';
+    }
+
+    /**
+     * Register the service provider.
+     *
+     * @return void
+     */
+    public function register()
+    {
+        $this->app['flarum.admin.assetManager'] = $this->app->share(function ($app) {
+            return new AssetManager($app['files'], $app['path.public'].'/flarum', 'admin');
+        });
+    }
+}

src/Admin/Middleware/LoginWithCookieAndCheckAdmin.php

@@ -0,0 +1,29 @@
+<?php namespace Flarum\Admin\Middleware;
+
+use Flarum\Core\Support\Actor;
+use Flarum\Core\Models\AccessToken;
+use Closure;
+
+class LoginWithCookieAndCheckAdmin
+{
+    protected $actor;
+
+    public function __construct(Actor $actor)
+    {
+        $this->actor = $actor;
+    }
+
+    public function handle($request, Closure $next)
+    {
+        if (($token = $request->cookie('flarum_remember')) &&
+            ($accessToken = AccessToken::where('id', $token)->first())) {
+            $user = $accessToken->user;
+            if (! $user->isAdmin()) {
+                die('ur not an admin');
+            }
+            $this->actor->setUser($user);
+        }
+
+        return $next($request);
+    }
+}

src/Admin/routes.php

@@ -0,0 +1,19 @@
+<?php
+
+$action = function ($class) {
+    return function () use ($class) {
+        $action = $this->app->make($class);
+        $request = $this->app['request']->instance();
+        $parameters = $this->app['router']->current()->parameters();
+        return $action->handle($request, $parameters);
+    };
+};
+
+Route::group(['prefix' => 'admin', 'middleware' => 'Flarum\Admin\Middleware\LoginWithCookieAndCheckAdmin'], function () use ($action) {
+
+    Route::get('/', [
+        'as' => 'flarum.admin.index',
+        'uses' => $action('Flarum\Admin\Actions\IndexAction')
+    ]);
+
+});