Chair not found - healing strategy

[chief-nerd]

Round/view breaks if a debate without chair exists. Make Debate::getChair() return the highest strength adjudicator in the panel and mark him chair if no chair is found.

[chief-nerd]

There is a follow up error that occurs if a debate without chair is published in https://github.com/JakobReiter/tabbie2/blob/master/tabbie2.git/frontend/controllers/FeedbackController.php#L173