add arc aggregator

Link: https://github.com/GeneAssembly/biosal/issues/520
Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
avoid actor access violation

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
configure kmer length for arcs

Link: https://github.com/GeneAssembly/biosal/issues/510
Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
fix name of graph store

Link: https://github.com/GeneAssembly/biosal/issues/510
Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>