Adding ability to use batch commands

This change adds the ability to run arbitrary batch commands.
This functionality is to be able to run windows commands on a windows
slave or master.  The format followed is exactly the same as the shell
functionality.

Change-Id: I463660b29b09e5945137b50b3721ee04cc5fc04c
Reviewed-on: https://review.openstack.org/19387
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Approved: James E. Blair <corvus@inaugust.com>
Reviewed-by: James E. Blair <corvus@inaugust.com>
Tested-by: Jenkins