Fix resource_class links in Rack listings

Fixes https://github.com/tuskar/tuskar/issues/55
Merge pull request #73 from jistr/bug/rack_list_resourceclass_links

Fix resource_class links in Rack listings
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
Added possiblity to update the Rack state

NOTE: This patch will not allow to set the Rack state
when creating a new Rack. The Rack must exists in order to update the state.
Merge pull request #76 from mfojtik/update_rack_state

Added possiblity to update the Rack state