engine: ManipulateAffinityGroup action group

added action group for all affinity groups CRUD commands
applied on cluster level.

For more information please refer
to: http://www.ovirt.org/Features/VM-Affinity

Change-Id: Ia460f65ded22197e3dc9ca594c66e76e04ce15fc
Bug-Url: https://bugzilla.redhat.com/1036638
Signed-off-by: Gilad Chaplik <gchaplik@redhat.com>