[Libvirt-cim] [PATCH 0 of 3] Fix offline VCPU representation

Currently, we cannot present information and instances for VCPUs when a domain is powered off, because virDomainGetInfo() does not work unless a domain is running. This set ultimately changes the vcpu bits in device_parsing to, that's right, actually *parse* the VCPU information from the XML like all the other devices, which gives us VCPU information for offline domains. To get there, I had to make the core of device_parsing a little more dyanmic so that the parsing modules could return mulitple devices for a given XML cycle, which vcpu needs.