Blender Git Loki

fix for annoyance found when looking into bug [#25226].

Changing the edge crease median value often wouldn't result in the median value entered because of clamping from 0-1.
Now the median crease is applied by scaling the values up/down.

also add some simple checks to speed up updates,
- don't move verts or recalculate normals if only crease changes.
- don't apply crease changes if location is being edited.