Adding master-slave MySQL backend.

Also fixed some issues:
  - Added runner.sls - meant to be used with salt-run state.sls.
    Orchestrates the ordering of master, slave, and auto
    restarting services of lsyncd once all web heads are up.
  - renamed role 'haproxy' to 'web-haproxy'. Might need
    an haproxy for db in the future.
  - file.absenting of /etc/apache2/sites-enabled/000-default
  - moved /etc/apache2/sites-enabled/default to sites-available
  - made symlink of above in sites-enabled
Merge branch 'master-slave'