Sorting source and headers while at it.

Moved update canvas signal to perspective load instead of hooking it to the paint event.
Added an "S" as the unit for the number of cells fact (as in 4S).

The goal of this first installment is to organize the code a bit so it's more readable,
clean up a bit of left over cruft, and manage link configurations (and links in general).

- Central widget no longer stacked. Views are added/removed to layout
to switch view
- Dock Widgets are globals with single instance of each type
- Both central views and dock widgets are just-in-time created saving
lots of memory

- Central widget no longer stacked. Views are added/removed to layout
to switch view
- Dock Widgets are globals with single instance of each type
- Both central views and dock widgets are just-in-time created saving
lots of memory

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.

The derived class wasn’t really adding any capabilties

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.