Improve Query-by-Gesture integration

[vogti]

Add a button in the right menu which opens a dedicated window showing the camera stream, the recognized gestures and additional instructions.

It should be possible to deploy, run and stop the Query-by-Gesture stack from within the UI.

The currently selected operator should be highlighted in the UI (e.g. by a green frame).

In Query-by-Gesture-Mode, the input fields in the operators should be replaced by select lists where possible.