LD term status page plus a bunch of LD fixes

Client-side page that fetches all JSON-LD context files, expands prefixed IRIs to full vocabulary URLs, and checks resolution in the browser.

This also motivated a lot of LD fixes. I fixed about 2/3 of the bad LD terms (from 310 errors to 107)

This will likely need a rebase after !30 (merged) gets merged.

Closes #34 (closed) (and then some!)