No functionality changes in this code, just code clarify improvements.

Remove signal overrides

QGCFileDialog can now be handled by unit test code

Turn off Windows Error Reporting for unit tests

This keeps TeamCity from hanging on a dialog box

Remove unused code

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

Simple MainWindow Unit Test

Splash screen is optional. Also remove some unused class definition.

New Unit Testing framework

Deployment target is still 10.6

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

Remove unused code

Link manager unit test and fixes

Fix linux compiler warning

Largest change is that once a link is added to LinkManager it maintains
ownership and is responsible for delete. If you need to delete a link
use LinkManager::delete. Also added guard code to assert if a Link is
deleted outside of LinkManager.