Feature/video player (#8)
This MR adds a VideoPlayer . It uses the dtkVisualizaitionViewVideo (on Mac) and dtkVisualizaitionViewVideoGL on linux
There is still a glitch on MacOS when there are two views (Video + 3D ): mouse mouvement in the 3D view makes the Video view garbage: flickering, mirroring, etc.
On linux, it requires gst-plugins-good and gst-libav (needed by qtmultimedia), available on the dtk channel