Purge on broken links within the (HTML) documentation. This mostly involves
deleting SEEALSO entries (where documentation doesn't exist) but also fixing a
few links.

Also fixed the anchor links in TheoryIndex.html and idIndex.html. In both
cases there aren't any entries starting with the letter "Y".

Update to EmitTeX. Some functions have been renamed and some help entries
have been added.

EmitTeX is no longer included in bossLib and is instead loaded using
end-init-boss.sml.