[et-mgmt-tools] [PATCH 3/3] Add storage volume creation wizard

[Cole Robinson]

The attached patch adds a storage volume creation wizard.

This wizard is simpler than the one for storage pools:
there is only one screen and fewer options. All that
needs to be specified is a name, format, allocation
and capacity.

There is some interaction logic that isn't present yet,
like disabling the name field for a disk volume, since
we should just choose the next partition name. However
it all works so it's in good shape to commit.

Thanks to Tim Allen for most of the UI design.

Screenshot:
http://fedorapeople.org/~crobinso/virt-manager/storage/vol-create.png

Thanks,
Cole