Generate HEAT template complete with definitions for host aggregates and flavors

* create aggregate per resource class, tag with name of resource class
* place all nodes of all racks in a resource class into it's host aggregate
* create all flavors, tag with name of resource class
* explained in https://www.pivotaltracker.com/story/show/53809435
Comment out all calls to Nova for managing flavors - this is now handled by the HEAT Template
Merge pull request #75 from marios/heat_template_flavors_aggregates_etc

Heat template flavors aggregates etc