add a case whare 5 particles are in one cell after some time
ADD replace_fn dummy
particle lies in quad doesn't depend on world
p4est_indent is only doing its job
set refine condition and refine every 1000 steps

ATTENTION this is choosen arbitrarely, because it fits this example.
Maybe this should be done in a dynamic way
refinement and coarsening handling

move all particles into their belonging childs
coarsen dummy
this should all be just debugging stuff
move particles from children to parent
typo
add DEBUG message
add coarsening
Merge branch 'coarsenAndRefine'