Support for keyframe based animation

We plan to merge Sequences extension features into Slicer core, so interpolation of any node will be available. If interpolation is implemented for a node then Sequence browser can use it quite easily. The main difficulty is to implement a simple yet powerful user interface. What is in Paraview or MITK seems to have taken a lot of work and still very hard to use.

If we need to change only one parameter at a time then we can easily add those as animation modes to screen capture module.

Camera animation is a special case, as you may not want to specify it by saving current camera positions as key frames, but instead by specifying a curve and maybe a look-at point. This can be managed in the endoscopy module. We should probably rename the module to something that reflects that it is a general “curve to transform” module (Camera path might be good, or maybe something even more general). We should update it to use the new curve widget, add option to export to sequence, etc.