engine, dao: Introduce ISCSI Bond entity, tables and dao

ISCSI Bond is the logical entity representing the group of networks and
the group of iscsi targets which will be connected by using these
networks. IscsiBond is used for configuring iscsi multipathing.

Change-Id: I12313c02810a2f0e75016bdd78b44da43f2154d4
Bug-Url: https://bugzilla.redhat.com/753541
Signed-off-by: Sergey Gotliv <sgotliv@redhat.com>