engine: add a per-actor dispatcher for message tags

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
implement Fangfang's block-wise partition scheme

Link: https://github.com/GeneAssembly/biosal/issues/108
Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>