Database:ify the list of security patches

Database:ify the list of security patches

This finally moves the patches into the db, which makes it a lot easier
to filter patches in the views.

It also adds the new way of categorising patches, which is assigning
them a CVSSv3 score.

For now, there are no public views to this, and the old static pages
remain. This is so we can backfill all existing security patches before
we make it public.