Convert app to flavored single app

[provokateurin]

This should make a lot of things easier, because we don't need the create app script anymore.
For web we will need a custom solution, because it doesn't support flavors.
Also a build script would be nice (something like run-viktoriaapp-debug.dart) to select the correct flavor and build target (main file which contains the respective app name and features).

[provokateurin]

Restructuring would also be a good idea. I imagine something like this:

assets/
	images/
	fonts/
scripts/
packages/
	app/
	utils/
	widgets/
	aixformation/
	cafetoria/
	calendar/
	ipad_list/
	substitution_plan/
	timetable/

(frame would be the new app)