So we unify parsing and building the XML. Since we already do this for vmmDomain, take the opportunity to move the shared infrastructure into vmmLibvirtObject
As outlined here: https://www.redhat.com/archives/virt-tools-list/2012-February/msg00040.html For now this is just a direct import of the code from virtinst commit dca5a4d6245f21d554f8853197a6a234bfc8e52c. History is not merged, so please refer to original git for detailed commit histor: http://git.fedorahosted.org/cgit/python-virtinst.git/