helpers: transition to new custom preferences (2/3)

Basically each visible element is now completely handled by
the new preference classes which hold the logic for setting
and element on boot.
Most XML-driven layouts are gone now, since it looks like that
android invokes a commit()-call on a XML-layout creation, which
is strictly against the new logic.

Although this changes quite a lot, no *actual* functionality change
happened until now, besides this there are however many small bug
fixes for various things.

Signed-off-by: Blechd0se <alex.christ@hotmail.de>