Added (UI) support for vehicles exposing more than one camera.

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.

For mobile, save log downloads next to where everything else is saved instead of straight into the home directory (which is anybody's guess when it comes to mobile platforms).

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

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

* Also handles correct prioritization of high latency links

Plus various bug fixes from flight testing

Implemented workaround for bug with qml property binding. Now the state of the checkbox will always match up with the state of the outputEnabled.

Joystick axes and buttons can now be monitored even when the
joystick input is disabled.

And fixes they found

Maintain a list of address/port pairs instead of a address/port map.

Minor improvement to detection of stick recentering after calibration. Without this if you performed a calibration with deadband enabled but one of the deadbands at the end of the calibration was ~0 it would be very difficult to position the stick so that Qgroundcontrol considered the axis to be centered.