Also distinguish Emergency Stop better

* Added support for sat count to Sensors check control

* QGCCheckListItem -> PreFlightCheckButton
* CheckList -> PreFlightCheckList

Automated preflight checklist: Initial commit. Note that this requires an autopilot firmware that writes the respective health flags in the SYS_STATUS mavlink message

Signed-off-by: Patrick J.P <patrickelectric@gmail.com>

Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>

Allow plugins to define a left placement for its custom flight widget.
When placed on the left, the action tool strip is placed on the right side.

Create a "Dead Mouse Area" control to eat mouse events underneath desired area. This is to prevent mouse events from leaking through controls underneath the area.
Replace original "NoMouseThroughRectangle" as this is more versatile.
Prevent mouse through events from leaking underneath the Fly View tool strip.

Adding missing qgcView to QGCMapPolygonVisuals instance in SurveyMapVisual.qml

Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>