Changes to CustomData: Some functions would only return the current active layer, added extra variants that take an index to select the level (modeled after CustomData_get_layer_n.) Still todo: * UVs are being interpolated linearly, should probably offer Catmull-Clark subdivision like Subsurf modifier. * Vertex Colors still don't support multiple customdata layers. * Editing UV data on levels other than 1 should be disabled in the interface (same for weights)