Blender Git Loki

Fix [#30419] Median wrongly setting lattice vertex weights.

In fact, the same bug affected curves' weights too. Now using the same method as for setting mesh edges' crease and bevel weights. Also factorized/simplified that part of code by defining a new utility func computing the scale factor.

Also greatly simplified UI code in same v3d_editvertex_buts() function, was really over-complicated (this fixes btw a few minor UI bugs in the transform editmode panel, like missing tips, etc.).