Upstream 2.13 + lots of packaging cleanups

Hi!

I've uploaded 2.13-1 to Debian experimental. Before I upload this to sid I would like some feedback from other people involved in src:apparmor maintenance, in particular about the deep changes/cleanup I did in the packaging, aiming at reducing the amount of distro-specific code we carry, with the end goal being to using the upstream systemd service (I've posted more details about my plans on https://bugs.debian.org/870697).

I would especially like you folks to check that I did not remove code that's still needed for some reason that I missed.

Please don't delete the source branch (debian/experimental) when merging :)