add actor model features

Signed-off-by: Sébastien Boisvert <sebastien.boisvert.3@ulaval.ca>
boot actors when starting the computation

Signed-off-by: Sébastien Boisvert <sebastien.boisvert.3@ulaval.ca>
allow messages to be sent between actors

Signed-off-by: Sébastien Boisvert <sebastien.boisvert.3@ulaval.ca>
fix the routing code paths for actors

Link: https://github.com/sebhtml/ray/issues/202
Signed-off-by: Sébastien Boisvert <sebastien.boisvert.3@ulaval.ca>