Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>

Moving methods from MainWindow to QGCApplication so that more things
can run without a window. Helpful for testing.

So no need for connect window close test here

Simple starting point to view testing

This was leftover from a problem I was having with virtual slots

Allows for UI unit tests to be written:
- Ability to respond to expected message boxes
- Ability to fail test if unexpected message boxes occurs

Used for unit testing