core: Add supportedEmulatedMachines to Host model cluster

According to http://www.ovirt.org/Cluster_emulation_modes,

Added a field to VDS - supportedEmulatedMachine

Added a field to VdsGroup - emulatedMachine

Added persisting those values to various procedures.

Bug-Url: https://bugzilla.redhat.com/927874
Change-Id: Ib12ef4a5289a72c1ea5a117c9c4f0435a7b6bafe
Signed-off-by: Roy Golan <rgolan@redhat.com>