Rudimentary support for the new orphan-packaging development model

Rudimentary support for the new orphan-packaging development model

Add a new --spec-commit command line option in order to support the new
package maintenance model of using separate packaging and devel
branches. In this model the packaging files (i.e. spec et al) must be
taken from other branch if the current branch is a development branch
(which only contains source code).

Change-Id: Ia8eb916dafd5bdc74c9b2d22591a8a36f6c11e95
Signed-off-by: Markus Lehtonen <markus.lehtonen@linux.intel.com>
Signed-off-by: Zhang Qiang <qiang.z.zhang@intel.com>