MATSim Code

more checks/tests and always add from the top of the tree

This somehaox fixes the problems... Though I do not see why it should
matter?
To investigate...

on emore check that intermediary state is correct...

check for topologival correctness of tree after each add

use a single value instead of a stack

stack would anyway only contain one single value...

add a check for cycles in the tree

use an "explicit" stack instead of recursion

maximum capacity

implement remove ( very inefficient )

bugfix

set sizes limitations