Sort and filter observation fields by count, place, and taxon

On https://www.inaturalist.org/observation_fields the following changes.

1 - on the page add a column of data that indicates the number of observations which use that field
2 - Enable sorting on the page data table so you can sort by name, count (from above) etc
3 - Add the geography and taxa filters onto the page so you can filter the list to see which fields are used for a subset of data.

See related:
https://forum.inaturalist.org/t/sort-observation-fields-by-name-in-user-interface/6363
https://forum.inaturalist.org/t/option-for-observation-field-queries-beginning-with/6373