Add batch_for_windows

Add a library used by osbash to generate Windows batch files that
can build a base disk and create a VM cluster with no dependency
other than VirtualBox.

Partial-Bug: 1312764
Implements: blueprint openstack-training-labs
Change-Id: I43cf5f47ac17b8292c5ce32a6849e89d1e192be3
Merge "Add batch_for_windows"