Disk Profile support (oVirt)

Added support to pull a list of all disk profiles from oVirt, and modified the volumes model, to allow disk profiles as an option. This branch requies the changes I made in the rbovirt branch of the same branch name.
Yeah, I have a pull request with rbovirt, as it stands now the current version of rbovirt does not have support for disk profiles, however no one is responding to my pull request. Here is the link:
https://github.com/abenari/rbovirt/pull/47. Thanks!