Partially or fully automated installations using Ubiquity

Ubiquity has some support for preseeding by virtue of using d-i as a backend. However, there is no support for skipping entire UI pages because they have been entirely preseeded. This should be fixed.

There may also be some call for a noninteractive (or at least non-graphical) frontend in the context of automatic installations. Investigate the use cases and determine whether this is necessary.