Try to make things so that image::opinsys makes the
standard opinsys-image, using packages::opinsys.
And image::puavo does the same for puavo-image (with packages::puavo).
Likewise image::thinclient and packages::thinclient.
Put "require apt::repositories, organisation_apt_repositories"
back to packages-class.  Saves lines and is necessary so
that "apt-get update" gets run before package installations.
Drop the plymouth_theme from the puavo image, and keep it in
"opinsys"- and "thinclient"-images.
Move plymouth_theme to a private repository (with name
ltspimage_plymouth_theme).
Remove ltspimage_lucid_nfs_compatibility.