Clean up when exactly we should save settings, and add in checks to make sure we do not do it incorrectly

This fixes a bunch of bugs with setting the title for widgets, deleting
widgets, etc.  It also reduces the amount of code duplication, which is
always a good thing.

Replace 9 seperate valueChanged() signals with just 1, and remove the resultant tons of code duplication

* The "Simulation" option is now not selectable.
* If the link is a simulation, then you can't change it to a different link type.
* The OPAL option is not shown if support is not compiled in.
* Fix the buddy, tab order and accelerators in the GUI.

This crash could be reproduced by starting QGroundControl, switching to
plot, then clicking the "Symmetric" checkbox.

This commit disabled RC RAW signal callback.