sub basin and river geometries need to accompany `MESH` setups for reference and clarity

[kasra-keshavarz]

There is a need to accompany sub-basins and rivers geometries with MESH setups. Drainage Database does not look to be a proper place for it, so it needs a bit of brainstorming. Any ideas appreciated.

[kasra-keshavarz]

Addressed in iss21 branch, will make a PR soon and close this.