Blender Git Loki

fixes for vertex color (found when brining X3D import back)
- tessface vertex color had the wrong sized array passing to rna_iterator_array_begin
- re-calculating tessface's would clear them if they were already created (own mistake)
- ED_mesh_color_add initialized tessface vertex colors from the loop color array

also made rna's mesh.tessface_vertex_colors.new() work like tessface_uv_textures.new()
where layers can be added as long as polygons are not present.