core: Add support for copied disk template

Add support for copied disk Template so an unregistered Template can be
registered with its copied disks

Change-Id: Id7514146d26792a361e47d1de820f5233ff9bf40
Bug-Url: https://bugzilla.redhat.com/1138136
Signed-off-by: Maor Lipchuk <mlipchuk@redhat.com>