Blender Git Loki

WIP: fancy wireframe display

Exploring some possibilities with wireframe rendering beyond solid
color.

New effect: color edges based on angle between the faces joined. Loose
edges, perimeter edges, and edges joining 3+ faces are colored
differently.

Some of this code will move to Workflow Shaders. Other parts will move
to DerivedMesh data requests �?? AdjacentFaces (struct) and/or angle made
by adjacent faces (float).

The (incomplete) shader version uses VertexBuffer�??s generic attribute
API, which we want to switch everything to eventually. There is a GLSL
vertex shader *not* included in this commit because I don�??t know where
to put it�?�

The CPU version is temporary �?? it�??s equivalent to the shader setup +
matching GLSL shader.

This particular effect is view independent, so can be done CPU-side
once and drawn many times. Other effects I�??m working on are view
dependent, so really need the setup + shader split.