[CONFIG]: Add transparent handle representing current command control
value.
[Config]: Linked input channel forms to correct UAVO fields.
[Input config] WIP: New sliders.
Increase ManualControllCommand update speed while showing live view.
No need to redeclare fontMetrics, it's already a class member.
Work around for Qt bug. On Linux computers, the `QPainter painter`
instantiation must follow QSlider::paintEvent(paintEvent)