Automate creation of both the nested VM and the main VM images.

Nested VM images to be built using buildroot. Builtroot configs, kernel config, and post-processing scripts should all be part of the build framework and part of CSIT git repository.

Main VM images to include three components:

• A packer template that creates a minimal disk image to be built one-time,
• A script that can be run periodically and that performs an "upgrade to latest" on the minimal disk image, and records the specific packages and versions that it's being upgraded to. These lists, in turn, should become part of CSIT archive
• A packer template that produces a specific release of disk image, taking a packet list (output from previous step) as input

Desired outcome is that, without the need for storing and archiving a large binary disk image itself, we have a framework that allows to:

• repeatedly build CSIT test images with either the "latest" or a historic/timestamped version, and functionally identical outcome each time
• make changes (add packages or other post-processing) and then rebuild with minimal amount of effort
• produces images with identical content for both CSIT VIRL (qcow2) and Vagrant (VirtualBox)