add a method to spawn actors to the actor class

Signed-off-by: Sébastien Boisvert <sebastien.boisvert.3@ulaval.ca>
add a Starter actor

Signed-off-by: Sébastien Boisvert <sebastien.boisvert.3@ulaval.ca>
move implementation code in cpp files

Signed-off-by: Sébastien Boisvert <sebastien.boisvert.3@ulaval.ca>