Mention Debian and Ubuntu as supported platforms
Allow creation of databases and users

Inspired by the Ansibles.mysql role.
Make MySQL root username configurable

While this doesn't seem to make sense on first glance it is useful for
systems which were screwed with Parallels Plesk, which renames the MySQL
root user to "admin".

This change allowes this role to be used while the server is
transitioning from Plesk to Ansible.
Make error logging configurable
Also adjust port and socket of the MySQL client