Allow requirements on 2- and 3- body topo output in B2OC prefilters

• update to prefilters.py / b2oc_prefilters() to allow the possibility of filtering on the 2 or 3 body topo decisions

• prefilters.py / topo_2or3body_node() is returning the or

• added the functions make_unfiltered_topo_threebody() make_filtered_topo_threebody() and refactored the code of threebody_line in topological_b/__init__.py

this last step was mandatory in order to have a simple implementation of prefilters.py / topo_2or3body_node()