Blender Git Loki

ShapeKeys: rework 'move skey' code, and add options to move to first/last position.

Main moving logic is moved to new `BKE_keyblock_move()`, which makes it available from anywhere.
In addition, move code was reworked so that it only loops once on whole keyblocks list,
and it accepts arbitrary org and dest indices, not only neighbor ones.

Partly based on work by revzin (Grigory Revzin) in his soc-2014-shapekey GSoC branch, thanks!