Remove old/ directory
Remove unneeded .ansible.cfg
Clean up README, add `play` wrapper script

This commit tidies up the documentation, and adds a wrapper script for
running playbooks from this repository, `./play`. This wrapper script is
intended to simplify the process of running ansible-playbook, without
having to perform large amounts of custom setup before you can start
work.

Notably, this also removes the "user" field from every entry in the main
playbook, so that each user runs playbooks as their own user, helping
with auditing and access control.
Remove unused handlers file
Clean up inventory file