invert connection is not canonical

Link: https://github.com/GeneAssembly/biosal/issues/528
Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
add actor for testing the walker concept

Link: https://github.com/GeneAssembly/biosal/issues/527
Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>