Process::nextStage

public function nextStage() // todo: rename to moveStageForward()
	{
		$next = $this->getStageIndexByCode($this->stage) + 1;

		if(!isset($this->stageOrder[$next]))
			$this->stage = false;
		else
			$this->stage = $this->stageOrder[$next];

		$this->step = 0;
	}