Refactor

Refactoring the playbooks to use the recommended 'roles' format. 

* Created 6 'roles' for organizing orchestration and config mgmt for the following
  - common-tasks (includes creating the dosomething user with ssh key, etc.)
  - mongo (spins up 3 new instances and installs mongo for a 3 member replica set)
  - nova (controls spinning up new servers for each of the other playbooks)
  - solr (as yet incomplete, will create a solr box with all affiliate indexes)
  - varnish (creates a varnish server box with Varnish installed)
  - webserver (creates a standard webserver box suitable for ds.org and running ds build)

* Mongo, varnish, and the webserver have playbooks that call nova to spin up servers, as dictated by the vars in the respective roles, and then install appropriate software.