Although the method is marked as thread safe in the docs, if you use a
database plugin it ends up not being thread safe.

Refactoring on MainWindow's view and settings code

- Use pkgconfig on linux to avoid break build on undefineds

Accel calibration wizard fix

Hopefully fix thread safety issue in opmapcontrol

Operator = is not thread-safe, but copy constructor looks to be. This
is causing an intermittent crash.

Renamed some variables.
Removed unused joystick settings stuff.
Deleted unused actions.

This function is called automatically when a QSettings object is destroyed,
so is rarely needed to be called explicitly.

There are still some cases where
a QSettings object is passed-by-reference, so there I left the sync() calls as
it's unclear how permanent those objects are and if they'd call sync() before
application shutdown

Fixes bugs with savings settings for the window state, theme, UAS-connected view, and low-power mode.
Also removes some unneccesary logic that attempted to handled unclean shutdowns, which I haven't
been able to reproduce.

It was a poor proxy for better coding around the problem of bad settings or the lack of
settings on first-run.

Correctly initialize floats as NaNs where expected.

Fix DISABLE_GOOGLE_EARTH

Fix broken connect

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