Channel Tracks use legacy field names

The channel track mapping table (npch.csv) is using legacy field names that need to be changed:
- **color_id** -> **np_color_id**
- **texture_id** -> **np_texture_id**
- **geometry** -> **np_geometry_id**
- **topo** -> **np_topo_id**

This requires a legacy method for loading chmap tables.