Multi Interpolation Editing of Tracks

[BryonLewis]

Capability to edit and move multiple boxes at once using the interpolation/track drawing feature.

If a user is tracking multiple items at once in a scene and would like to track a box, move to the next frame and modify the box it would be easier if a number of selected boxes all provided outlines to move on the next frame instead of a single box. With a single box a user has to go through the frame time multiple times to track all objects. Adding in multi-select would allow the annotator to only have to go through it once.