_messages_model added to Program model.
_messages_model added to Program model.

It was defined only for module specific programs, i.e. GCIProgram and GSoCProgram, but it makes sense to set it for the parent class to, general ProgramMessages are also defined on that level.

rhyolight/nupic.son,rhyolight/nupic.son,rhyolight/nupic.son