Add first image recipe: integral-image-ndvm-pkg

This is the best method I've come up with to get images copied into
other images. I considered "just bashing it" in the top level build.sh
script from oe-build-scripts.git which felt like a hack and will
make for weird dependencies between different build trees. I want
this to be as parallel as possible and I'm anticipating many
supporting VMs. I wanted worst-case to be parallel builds for all
service VM images and one additional build for the image (dom0 or
an installer) that consumes the service VM images.
integral-image-dom0: Depend on NDVM image package when INTEGRAL_EXPORT_DIR is defined.
integral-image-dom0: Use base_contains and a distro feature to add dependency on the NDVM image package.

Using base_conditional to detect the setting of INTEGRAL_EXPORT_DIR
wasn't flexible enough. If we want dom0 to itself be made into an
image package we'll have to define INTEGRAL_EXPORT_DIR but having
used base_conditional this will cause dom0 to pull in the NDVM which
we may not want.
Add new distro for a dom0 live image.

This will be a dom0 with all of the supporting VMs packaged in it.
This allows us to use the existing integral-dom0 distro to build a
dom0 with no service VMs in it for when the installer pulls in
dom0 and service VMs itself.
integra-dom0: Consolidate common configs for integral-dom0 distro variants.