Make sure mizuRoute input file tools can be used for Paleo work

[ekluzek]

This is an extension of #446. The mizuRoute tools will need to be evaluated in the Paleo context to ensure they can be used for CESM Paleo users for CESM4. In order for mizuRoute to be the one River model for CESM4, the input files tools need to work satisfactorily for Paleo work.

[ekluzek]

Part of what this means is to have tools in mizuRoute that will take a low resolution DGM for Paleo work with a different land mask and create the mesh, mapping files, and network topo input files that mizuRoute needs to run for that case.

Paleo work usually uses a regular half degree grid for their work (since you can only guess at the elevations it makes sense to use a low resolution). This means for Paleo work the mesh would likely have to be a regular half degree grid and not a more elaborate basin catchment map. There might be some limited cases where catchments have been worked out for Paleo work, but I'd assume that's the exception and not the rule. And I'd guess that's only been done for a limited set of more modern cases.