Fixes various multi-touch interaction issues
Panning was compounding the translation causing a pan that would scale exponentially as it progresses.
Pinch gesture was being handled by printing an error message.
There was no "end" to the multi-touch events.
This MR also moves up the [Set/Get]CurrentGesture
methods to the vtkRenderWindowInteractor
from its derived class vtkVRRenderWindowInteractor
Edited by Sankhesh Jhaveri