render_to_response does not work on newer django, so it needs to be
replaced. And using a speicfic context actually overcomplicates things,
it's easier to just use a wrapper function. For those cases where we
don't need NavContext, just use render() (the new shortcut function from
django), which also removes the need to use RequestContext.
That just generates a completely empty page in the output, so remove the
link completely instead.
For supported versions we list all of them, including if they have no
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.
