Categorize glossary

[padiwik]

Aside from moving things around, the only edits I've done was to add a term for "forward-solve" and add the synonym "randomgram".

[betaveros]

Sorry, this conflicts too horribly with existing changes to merge; I'm also still not convinced that categorizing the terms is useful and can be done neatly for every term. But something I might consider is some kind of tagging mechanism that lets people dynamically filter for terms in a category or something like that, which would also allow for overlapping categories.

[betaveros]

(I incorporated the edits, though — thanks!)