core: VM and VDS implement Nameable

VM and VDS implements Nameable so they could be referred by
the Nameable.getName() property, regardless the concrete class
type of the entity.

Change-Id: I7c3953e0651f2e9c843d041cdc37090ad37e87e1
Signed-off-by: Moti Asayag <masayag@redhat.com>