Move initialization into Uranium's run() function

This makes it possible to start a Uranium-based application without needing to know the magic incantation of starting the application.

cura/CuraApplication.py

@@ -669,6 +669,7 @@ class CuraApplication(QtApplication):
         self._plugins_loaded = True
 
     def run(self):
+        super().run()
         container_registry = self._container_registry
 
         Logger.log("i", "Initializing variant manager")

cura_app.py

@@ -134,11 +134,4 @@ import Arcus #@UnusedImport
 from cura.CuraApplication import CuraApplication
 
 app = CuraApplication()
-app.addCommandLineOptions()
-app.parseCliOptions()
-app.initialize()
-
-app.startSplashWindowPhase()
-app.startPostSplashWindowPhase()
-
 app.run()