FW Landing Pattern: Support for stop photo/video. Plus item unit test.

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

Also turn on MavlinkLogTest

Instead us a Toolbox concept which hangs off of QGCApplication

Changing the order of the QGCFileDialog::getSaveFileName() function. The idea was to expand the existing QFileDialog version but as we removed the selectedFilter, we might as well make this more intuitive. The options argument is the one trully optional and should be last.
Adding an example to the documentation on how to go about figuring out what file type was returned by these functions.

Removed the “selectedFilter” argument from the QGCFileDialog functions along with references to it in unit tests.
Fixed function declarations and prototypes formatting while at it.
Changed the caption of a few file save dialogs with a more descriptive text (explicitly telling what is being saved).

WIP issue #1173. Adding default suffix (extension). While at it, added selected filter support and removed unit test assert about its use.

Plus a large number of other changes to allow for orderly shutdown of
objects without crashes or asserts. This is need for unit tests to
create/delete global state around every test.

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