Fix license & etc

ubuntu -> bionic
debian -> stretch

just run ```build.sh Dockerfile.debian``` instead

publicize repo signing key as part of startup, previously
was only doing this at the end of the update_mirror.sh script

swiching to xenial should be as easy as modifying the dockerfile
and updating the update_mirror.sh script

also a minor change to aptly graph in update_mirror.sh

mirroring all open source components makes the mirror more useful

the repo key wasn't in the right directory so it wasn't accessible
through nginx

the original update_mirror.sh only allowed for mirroring the main
repository. left out restricted, multiverse, etc. the component is now
an array so it is easy to add additional components if you want to mirror
more than just main

If the .gnupg directory doesn't exist and we try to import keys
gpg won't be able to import the keys on that run, running --list-keys
first sets things up before we try to import