conditional splitting with new question splitting option

When splitting a non-matrix type question, it might make sense to have a
parameter specifying HOW/WHEN to split. So you could prevent a two answer
category question (yes/no) to be distributed over two pages. Maybe something
like "split_min", only split if splitting is on and a question has more than
split_min (eg. 5) answer categories.

as suggested here: http://bugs.limesurvey.org/view.php?id=8344