Instrument Animation RFC

This RFC is a proposal to allow nested animation via groups in the panel/instrument system.

Under this proposal:
 * Groups would have an animation mode, which would be one of: none, rotation, or translation.
 * If a group's animation mode was not "none" the group would have a primary dataref and key frame table. The key frame table's output would be in pixels (translation) or degrees (rotation).
 * If a group's animation mode is translation, the group would also have an "axis" property defining the direction of translation (as a DX, DY).
 * All sub-groups and instruments within the group would be affected by the animation.