main: move most of main to app, separate ownership

main: move most of main to app, separate ownership

* Move everything apart from the display connection itself to App.
* Everything depending on the display however is owned by App.
* Dispatch events for the application in App::dispatch_events()
That is, display_dispatch and local stuff e.g. execute_pending().

Signed-off-by: Marcus Fritzsch <marcus_fritzsch@mentor.com>