aurweb dev playbook & fixes for aurweb playbook

aurweb role:

• Make sure that we install gunicorn and uvicorn
• Move python module installation:
  We need some modules to be installed before doing the DB init. (alembic)
• Remove double entry for starting aurweb-git-archive.timer
• Link update wrapper after creating git repo
• Fix permissions for cgit deployment
• Refactor aurweb role variables

root_ssh role:

• Add possibility to add additional ssh root keys

aur-dev.archlinux.org playbook:

• New playbook for aur dev machine(s) ("review apps")
  Goal is to spawn and provision a new VM with aurweb when an MR is created
  See: https://md.archlinux.org/devops-agenda-27-july#