Constrain selection of parcels to areas with underlying data

[davemfish]

There are no constraints over which parcels a user can select and add to a study area. The parcels cover the entire US. But other underlying datasets have much narrow coverage right now. These include,

• LULC raster
• ACS tracts
• The citywide invest results that will be the basis for equity metric comparisons

We should guard against someone creating a study area that is wholly or partially outside the bounds of the underlying data.