Blender Git Loki

NLA SoC: Transform tools for NLA

This commit restores transform support for NLA. Grab, scale, 'extend', and tweak (i.e. grab by just click+dragging) are implemented.

Notes:
- As soon as one end of a strip touches another adjacent strip (within the same track), that end stops moving. This has been done to avoid the situation where overlapping strips within the same track (which is not allowed) might be caused by transforms.
- Made some changes to the RNA setters for the strip extents so that the validation above could take place (and other necessary changes on a per-strip basis could also occur).

TODO's ?
- Strips cannot be transferred from track to track using transforms. I've yet to decide whether this needs to be done, or whether a separate operator will suffice.
- What happens to the range of Actions used when the strips change sizes unexpectedly (i.e. the no-overlap condition above)? Currently range stays the same, but this doesn't always seem desirable?