In accordance to what was discussed in #3, this implements a PGF Key to steer the multi page layout, page layout. Per default, it is not used. When it is used, the option to the key is directly passed to \pgfpagesuselayout{OPT}, for example \fzjset{page layout=2 on 1}.
Since the page layout is actually different from handout, I removed the \mode<handout> part from the key's definition. Users should rather wrap the \fzjset call in the \mode<handout> macro.
The tutorial has been changed to reflect (and explain) that; the minimal_handout.tex file changed as well.