Blender Git Loki

Keyframe Defaults and Cleanups:

This commit fixes reports #21638 and #21818, which were both also Durian feature requests.

Cbanges:
* Added new default setting for the type of handles created when creating keyframes. This can be found in the user-preferences, and is used whenever existing keyframes aren't being overwritten (instead of the value being always taken from the keyframes either side, #21638).

* When keyframing over existing keyframes, only the values will be changed. The handles will be offset by the same amount that the value of the keyframe changed, though how well this works in practice still needs to be tested more thoroughly (#21818, already fixed earlier, but this commit is the full fix).

* When 'free' handles are added by default, they are offset to be +/- 1 frame on either side of the keyframe so that it is obvious that they can be moved. However, they just take the same value of the keyframe since this is easiest.

* Properly initialising handle colour defaults for 3D-View and Graph Editor. Graph Editor's theme userprefs also show these settings now, though the layout is really quick hack-style.