Adding changes to OpenStack CPI for volume type.

Adding the following functionality to the OpenStack CPI:

* Switched from the compute to the volume API for persistent disk creation
 * Creating volumes from the compute API is deprecated in OpenStack
 * The volume API adds support for availability zones and volume type
* Adding availability zone support to the boot_from_volume functionality
* Added support for the new cloud_properties to set the volume_type from disk pool configuration

This is due to the differences in fog between the compute/volume model (https://github.com/fog/fog/blob/master/lib/fog/openstack/models/compute/volume.rb) and the volume/volume model (https://github.com/fog/fog/blob/master/lib/fog/openstack/models/volume/volume.rb).  I'm not sure why they used names in the compute model that don't match up to the API, but you can see in the request that they changed it back before submitting it to the API (https://github.com/fog/fog/blob/master/lib/fog/openstack/requests/compute/create_volume.rb).

The code change I submitted included switching to the volume model to get support for setting the volume_type, so I needed to change the attributes being passed to fog to line up.