packaging: Changes for official builds

Made engine name and smbios values configurable and moved out
hard-coded values into configuration script:
 * registration URI
 * qemu-kvm/qemu-img package names.

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1119020
Change-Id: Iae2854badc6b33073aa1d30e014172a3788057b5
Signed-off-by: Dima Kuznetsov <dkuznets@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/30747
Reviewed-by: Alon Bar-Lev <alonbl@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>