connect "Run Scenario" button to backend to actually kick off scenario run

[mt-digital]

This will require a few things:

• [x] update POST /api/scenarios route to use @jerickson42's PRMS parameter modification tools
• [x] update tests to show changes in parameters; currently tests just test that routes work
• [x] run PRMS locally on the server (precursor to using Moinul's modeling service)
• [x] jquery to run POST request on click
• [x] ingest statvar.dat basin_cfs as streamflow for hydrograph. see https://github.com/aleaf/GSFLOW_climate_utils/blob/master/PRMSio.py#L330 for an idea

Scenario list should work as expected to update after scenario has finished running.