Integrate `ROMS-Tools` river forcing

[NoraLoose]

ROMS-Tools can now create river forcing. Going forward, we have to complete two more steps:

• [ ] Test whether the river forcing created by ROMS-Tools actually works with UCLA-ROMS. (We have seen all kind of surprises in the past.) Here, we should test whether both of the following river forcing types work:

  
  from roms_tools import RiverForcing
  from datetime import datetime

monthly_river_forcing = Riverforcing( grid=grid, start_time=datetime(2012, 1, 1), end_time=datetime(2012, 12, 31), convert_to_climatology="never" ) climatological_river_forcing = Riverforcing( grid=grid, start_time=datetime(2012, 1, 1), end_time=datetime(2012, 12, 31), convert_to_climatology="always" )

@dafyddstephenson maybe we can test this on your Wales domain, assuming it contains at least one river? (I can do this, but have to remember how to run ROMS without C-Star again. :D)
- [ ] Integrate the river forcing capability into C-Star.

[NoraLoose]

It does contain multiple rivers from the Dai and Trenberth global dataset!

Here is the climatology:

Here is the monthly river forcing. Looks like all Wales rivers have missing values in 2012, so the river volume flux is set to zero for all rivers. Poor Wales!