Meza/Install on multiple servers

Below is the basic procedure for setting up a multi-server environment using MediaWiki. I other words, rather than putting all components of a MediaWiki setup on a single monolithic server, this will split them out split them out over two or more servers. This means you can have separate servers for database master, database replicas, Memcached, Parsoid, Elasticsearch, load balancers, and MediaWiki itself. After some initial setup, Meza handles the orchestration of all of the servers for you.

Definitions

 * Controller: The server running the commands telling other servers what to do
 * Minions: The other servers. These will end up being MediaWiki application servers, database servers, Node.js servers, Elasticsearch servers, etc.

Setup controller
At this time it is recommended that your controller also be an app-server. This recommendation will be removed eventually.

Troubleshooting
If the `sudo bash /opt/meza/src/scripts/ssh-users/transfer-master-key.sh` gives you something like `Permission denied (publickey,gssapi-keyex,gssapi-with-mic).` It may have to do with ssh-agent forwarding and access to the minion. Assuming you can `ssh` to the minion, here's how to perform this step manually.