engine: Introduction of command entity dao

Introduction of command entity database support
(upgrade script, stored procedures, DAO, DAO tests)

Add persistCommand and retrieveCommand to
CommandCoordinator interface. The retriveCommand
rebuilds the command heirarchy.

Change-Id: I463102d85de7558fbcab23585ad6b48cdc35c0a0
Bug-Url: https://bugzilla.redhat.com/1083769
Signed-off-by: Yair Zaslavsky <yzaslavs@redhat.com>
Signed-off-by: Ravi Nori <rnori@redhat.com>