db: Affinity Groups database support

* Create affinity groups and members tables
* Add affinity group view (join of affinity group and members)
* Add CRUD stored procedure for affinity groups, the procedures
will control both of the tables, i.e. insert affinity group, will
fill its members as well.
* Stored procedures for fetching Affinty Groups:
  * by id
  * by cluster id
  * by vm id
* dao Tests

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

Change-Id: Ib09c50cae8d9a23a08a9e723d0e0498ea2016e6a
Bug-Url: https://bugzilla.redhat.com/1036638
Signed-off-by: Gilad Chaplik <gchaplik@redhat.com>