smooth out last few rough edges with GEO-PEAS

Finishing with the GEO-PEAS service there are a few small details that need to be refined.

~~Landcover

The entries in the controlled vocabulary are not matching with the data used in the service.~~

Ecoregion

The service still returns the OBJECT_ID instead of the ECO_ID. The controlled vocabulary uses the ECO_ID.

NOx emissions

The pages have a query for year 1990. The earliest available year in the service is 2000. rename mean_nox_emissions_10km_year1990 --> mean_nox_emissions_10km_year2000

Mismatches between database field name and url

srtm -> topography_srtm
nightlight -> stable_nightlights