Enhance image delivery experience of desktop application

This MR does not affect web applications because they set view.Display = false

Earlier, we rendered an image upon arrival of a packet from the render service. The interactor would immediately do another render that retained the previous image because interactor->EnableRender is true by default, simply turning it off doesn't sit right with the QVTK-pq layer. These steps caused a sticky feeling in desktop apps, as a whole, it made the desktop applications very off-putting.

We address that problem by queuing up the packets for later decoding and display. It happens eventually when the interactor wants to render. By carefully controlling when to swap buffers (win->SetSwapBuffers), the desktop experience is somewhat better than before.