[Catalog-sig] start on static generation, and caching - apache config.

["Martin v. Löwis"]

> So no race condition.

What Phillip says: "the update code" has a race condition,
if multiple simultaneous updates occur.

My proposal is still to put a table into Postgres that lists
the pages to regenerate. The (single) update process would
lock this job table, clear it, release the lock, and start
generating; alternatively, multiple update process would each
lock the table, generate, then release the lock.

Regards,
Martin