Blender Git Loki

Multi-Objects: Initial select similar support

Note: I had to add an epsilon on top of the threshould for SIMVERT_NORMAL.
Otherwise I was getting differences such as 0.000000something when comparing
supposed-to-be-identical normals.

The way I see it, the Threshold option is a user feature, where users can
control more or less what they want selected. While the epsilon is a
non-negotiable requirement for our float comparison here.

This includes support for:
* SIMVERT_NORMAL
* SIMVERT_FACE
* SIMVERT_EDGE

Not included and currently not supported/disabled:
* SIMVERT_VGROUP
* SIMEDGE_*
* SIMFACE_*

While we are working on this, we prevent users from using the non-ported modes.
Note: the bmo_similar.c file is still around, to be removed in the near future.

Everyone: Please fell free to jump in and help tackling the missing modes.

For details on the implementation discussion:
https://developer.blender.org/D3674