Document the requirements of the "delphix-entire" package version

[prakashsurya]

With the changes being proposed here to the virtualization application, the format of the "delphix-entire" package will need to adhere to the assumptions made by the virtualization application.

Thus, we should document these requirements, and probably also put some verification in the logic that generates the "delphix-entire" package to ensure we adhere to these requirements (and fail in the build when these requirements aren't met, rather than failing during upgrade).