coloring: added comments for coloring subsystem

Reviewed-by: Pier-Luc Plante <pier-luc.plante.1@ulaval.ca>
Signed-off-by: Sébastien Boisvert <sebastien.boisvert.3@ulaval.ca>
update release procedure

Signed-off-by: Sébastien Boisvert <sebastien.boisvert.3@ulaval.ca>
next release will be 2.3.1

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