Introduce new DI container

- Adding Friendica\DI class for getting dynamic classes
- Replacing BaseObject::getApp() with this class

src/Module/ToggleMobile.php

@@ -3,6 +3,7 @@
 namespace Friendica\Module;
 
 use Friendica\BaseModule;
+use Friendica\DI;
 
 /**
  * Toggles the mobile view (on/off)
@@ -11,7 +12,7 @@ class ToggleMobile extends BaseModule
 {
 	public static function content(array $parameters = [])
 	{
-		$a = self::getApp();
+		$a = DI::app();
 
 		if (isset($_GET['off'])) {
 			$_SESSION['show-mobile'] = false;