Adding Phosphorous data to the trends dashboard

[Vismayak]

Alejandro''s Phosphorous data has its own shapefiles and stations, for now add two geojson files with the data and query them to create new stations and watersheds

[Vismayak]

First implementation is done but here are the following bugs to correct:

• [x] P watersheds not showing
• [x] Switching between nutrients need to reset selections