MATSim Code

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

maximum capacity for quadtree

not yet fully implemented (should actually be possible to never
addelements that should be removed afterwards)

revert capacity doubling

32 768 friends should be enough, and I do not have time to write tests

add maximum size

we know our target degree: no need to store 1000 potential friends if
target average degree is 20...

fix compilation failure