Working plane visual hint

From this iteration we implemented as feature a visual hint drawn as a circle shape, hint that shows the plane where the user draws.

Worked at improving the hint drawing and also added at DrawingInterpreter a property that allows the coder to disable selection on a drawn shape so that the hint is not detected as being a shape from scene. The code is finalized but there are some issues with OpenCascade selection disabling, it seems that it doesn't work well.