ManageIQ model changes for vendor specific methods.

Changed Method class schema to add vendor specific methods and
relationships.
Added red hat, vmware, amazon, openstack specific provision methods.
Changed method instances to call vendor specific methods.
Changed VMProvision_Template and VMProvision_VM schema default values
to pass vendor name as message where appropriate.
Merge pull request #416 from tinaafitz/automate_vendor_split

ManageIQ model changes for vendor specific methods.