more complex test case for dist_matrix()
use numpy mechanisms for get_max_dist_pair()
mask the reference id in find_neighbor()
tests for find_neighbor()
tests for path_greedy()
tests for cut_extrema()
tests for sort_neighbors()
generate "real" masks instead of 0-1 lists
remove old, buggy and useless build_filament_mask()
rename gen_mask() to make_mask_by_index()
tests for tesselation()
remove vertex list from tesselation()

this was a historic leftover from debugging and does not server any
obvious need, so we discard it completely
more error checking, additional tests
minor cosmetics in test code