Jessie desktops

just opening this for review, comments welcome

still 3 major issues left that I'm aware of:

* d-i asks non-preseeded question (rt#3049)
* udev names network interface eth1 (rt#3050)
* puppet-trigger doesn't work on jessie (rt#3052)
Removed in f37c54137e04d01cb9c61425a921c7c7c735611d