* Drop ZMQ as the communication mechanism between job_event_callback and
callback_receiver
* Setup queue and exchange for callback broker communication
* Refactor event plugin and callback receiver to efficiently handle
message submission and processing
* Integrate django caching for parent processing
* Vendor ansible's azure_rm inventory script
* Add new inventory type
* Add new credential type
* Expand host instance_id column from varchar 100 to 1024 to accept the
long instance ids returned by Azure
* Make the inventory_import azure match rename more explicit.
* Break requirements down into ansible and tower reqs
* Generate separate Ansible and Tower virtual environments
* Install appropriate requirements files into each one
* Modify development tools to use these venvs instead of our old
site-packages
* Modify settings to indicate venv enablement and location of venvs
* Modify tasks to use the proper virtual environment for its purpose
