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>

Joystick: Fix calibration and default use: Do not send anything to vehicle until enabled. Enable after calibration by default.

Instead us a Toolbox concept which hangs off of QGCApplication

- select active vehicle
- arm/disarm
- select flight mode

When on Joystick config page:
- Not calibrating: If joystick is enabled, joystick messages should
continue to go to vehicle