Now works for more than Serial links

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

Summary page is also the launching spot for the setup screens. No more
left hand set of buttons.

When using DeleteOnClose with a QQuickWidget, the shutdown sequence
causes the MainWindow destructor loop back onto itself.

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.

The derived class wasn’t really adding any capabilties

Also moved log file settings save check to mavlink protocol

Also only update the full tree one time once the full parameter list is
ready.

Previously link were just destroyed

This makes unit test output easier to read

Previously link were just destroyed

This makes unit test output easier to read

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.