Preinstaller

Support preinstallation of laptops and wirelessaccesspoints. Once a preinstalled host is booted the first time, it should be registered for some particular organisation and then after a reboot it can actually be used.

Plus some other changes and improvements, such as a user interface for choosing preseeds, preinstallation and making installation disks. Preseeding works with preinstallation as well.

Needs a merge for puavo-client from its preinstaller branch as well.