Walrus add location

[sverhoeven]

Walrus does not know where it is modelling. BMI offers get_grid_origin() and get_grid_spacing() methods for
uniform-rectilinear

Add bounding box to config file so the get_grid_origin() and get_grid_spacing() methods can be implemented

[sverhoeven]

For Hupselse beek some locations:

• Centroid: "coordinates": [ 6.65443600418465, 52.06132311280826 ]
• Extent: "MINX": 6.6284541343879164, "MINY": 52.044712927740704, "MAXX": 6.6796664734187621, "MAXY": 52.07377683038932

Or see https://github.com/eWaterCycle/TerriaMap/blob/master/wwwroot/datasets/walrus-hupsel.geojson for shape.