Blender Git Loki

SetSplitNormals modifier: add a new 'from split normals' mode.

This adds the ability to set our split normals from target's split normals.
We first find closest vert, then select 'best' lnor by matching polys' normals.

Note that if target has stray vertices, modified lnors closest to those non-loop
target vertices will just get auto-normals. Not sure we want to add further
loops to find closest 'loop-compatible' vert?

Also, fixed a nasty dummy crash when swithing target to Edit mode!