WIP: Separated miniboxing from duplication

Pretty big change, we now have 5 transformations:
 - miniboxing preparation (add minibox2box for args, add box2minibox to return)
 - duplication
 - miniboxing intermediate values (val x: Tsp = ... => val x: Long = box2minibox(...) and adaptation)
 - miniboxing method and select rewiring, in the future also parent rewiring
 - miniboxing peephole reduction (reduce minibox2box(box2minibox(...)) aso)
Fixed tiny bug -Ycheck:minibox was complaining about
Closes #9 and doesn't seem to open others :)

Today's lesson: using the dedicated infrastructure isn't always the best thing...