Add pagination for the glossary

[m-iancu]

Keep a way to see the full glossary in one page. But, by default it should use pages for quicker rendering (glossary size is >25M already and growing).

[kohlhase]

we have been talking about pagination in the keyrex meeting @aoripov please assign this issue to whomever it was given there.

[kohlhase]

BTW, it is not entirely clear what kind of pagination we want to have. We might want x-entries/page or we might want alphabetic pagination. Probably we want to have both in the long run.