Add MariaDB Role (with galera clustering)

This primarily adds a new role for installing MariaDB for non-RDS instances and add active/active galera clustering as an option for running a load balanced and HA mysql cluster.  It borrowed quite a bit from edxlocal for user creation.

In addition to the new role I also made a cluster vagrant that stands up three boxes and installs all our cluster capable roles.  If you guys want me to split this in two, that is fine with me, but I used the cluster vagrant to help build the role so it ended up on this branch.

The cluster members need to be able to talk to each other as well, and it also allows the app to connect. Removing it sets it to all interfaces