metapackages are expanded into a list of its dependencies.
This achieves two goals:
- the installer shows which packages will be installed
  together with the metapackage
- after deleting meta package, apt-get autoremove not
  will remove its immediate dependencies

This enables examples in qt-creator.

This commit is actually a rework of what's been done
in RELENG-e2k-workstation private branch (along with
a few more generic fixups).

...and move lmms to disk.

- Merge base and desktop
- Remove all specialized software from LiveCD
- Move biggest education applications to appropriate group lists