Filters for exploring certain categories/tags

While our entry form collects things like scientific discipline & type of the POI, we're not using this data so far. Instead, so far, the map always shows all data points.

Start by locating the entry form fields for scientific discipline and POI type, then trace where the map loads and displays all data points. Add a way to filter the map by the collected categories or tags, and verify that selecting filters changes the visible data points while leaving unfiltered viewing available.

Written by the indexing model from the issue text.