There appears to be a threading issue in qRegisterMetaType which can
cause it to throw a qWarning about duplicate type converters. This is
caused by a race condition in the Qt code. Still working with them on
tracking down the bug. For now we register the type which is giving us
problems here while we only have the main thread. That should prevent
it from hitting the race condition later on in the code.

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

Simple starting point to view testing

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.

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

This keeps TeamCity from hanging on a dialog box

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

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