App messages now use simple modal message dialogs. Vehicle messages continue to use non-modal popup.

Move ArduPilot preflight check handling to generic QGC

Prompt for Reboot after compass cal

There are many ways of iterating over lists in C++/Qt.
In the specific case of QStrings, it is known [1] that using
foreach with const references avoids the creation of new
QString objects in each iteration, reducing the time consumed
by the loops.

[1] https://blog.qt.io/blog/2009/01/23/iterating-efficiently/Signed-off-by: Anselmo L. S. Melo <anselmo.melo@intel.com>

This fixes rotate images showing up at the wrong time

- MultiVehicleManager is a Qml friendly replacement for UASManager
- Vehicle is a replacement for both UAS and AutoPilotPlugin

QGCUASParamManager and friends are replaced by FactSystem

- cancel support
- mag rotation images
- set board rotation before cal
- set compass rotation after mag cal