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

Otherwise we can end up generating strange CRCs.

- Also corrected system/component id usage
- Switched to new Qt5 connect api

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.