LTSP improvements for quantal

General discussion on improving LTSP's integration in Ubuntu and our overall thin client experience.
Ideas that have been mentioned and should be discussed:
 - How to deal with chroot upgrades (currently not supported)
 - Making maintenance easier
   - Split ltsp-live out of the main ltsp package
   - Rebase on Debian's packaging for ltsp itself (only package we don't simply sync at the moment)
 - Generating a .img image from an LTSP chroot that can be used to make a standalone thin client image

Stéphane, please fill out the below section with an explanation of this feature that would be appropriate to include in the Ubuntu release notes.

Release Notes:

Work items:
[ogra] Add support for .img building into ltsp-build-client (code at http://paste.ubuntu.com/936878/): POSTPONED
[stgraber] Add support for ARM into LTSP upstream (generating the missing glue to allow ARM booting): DONE
[stgraber] Investigate enabling recommends by default in ltsp-build-client (done upstream): DONE
[stgraber] investigate zram or whatever the flavour of the year ram cache thingy is (bug 1031482): DONE
[jonathan] update LDM themes to new Ubuntu themes: POSTPONED
[alkisg] Ensure that all our LTSP hooks have been moved to ltsp-live so that upgrading the chroot works: POSTPONED
[jonathan] add a preseed option so that ltsp-build-client can be called with --fat-client in d-i: DONE