Added the possibilty to see only one UAS at the time with the drop down menu after clearing the view

No major functionality changes.

Also uses new min/max/invalid widget display

also adds AMSL output in ft

- Updated to use RCChannelWidget
- Removed attitude control widgets
- Previous calibration values now shown when not actively calibrating

Left QGCRadioChannelDisplay alone so that I didn’t need to modify all
the other APM board code which uses this control. Also new control only
support horizontal orientation, with no plans to add vertical.

Path through code allowed for xmlfile to be used when file was not
opened. Also changed qWarning->qDebug to allow QT_FAIL_WARNINGS to be
used to find bugs.

This way we can test with QT_FAIL_WARNINGS set.

Plus a few API tweaks

Also updated to latest QGCUASFileManager implementation.

Tried to order items in order of importance.
Also all perspectives now have their own shortcuts.

Both on the backend (replaced with DEFAULT view) and on the front end (removing UI menu items).

Includes removing an if-statement that should've been dead but was erronously applied to the following statement. Dead code = bad, if-statements without braces = bad.