Blender Git Loki

Object constraint lines viewport drawing

The core logic of this implementation comes from the drawobject.c from 2.7x.
I'm using `ts.colorGridAxisZ` for its color because of the legacy code:

```
UI_GetThemeColor3ubv(TH_GRID, col1);
UI_make_axis_color(col1, col2, 'Z');
glColor3ubv(col2);
```

There is nothing stopping us from adding this to the theme though, as it should
have been the case to start with.