This ensures that carbons will be activated again.

So that it shows unread messages upon page reload.

* added change #894

* #894 - fix jid comparison in setAffiliationAndRole

when already scrolled up.

instead of having them already in the templates.

It doesn't always create a new room.

So that when a room is closed, a previously obscured chat doesn't become
visible again. Allowing this would force us to know which chat is visible, so
that we can falsify it's `hidden` attribute.

otherwise also the prototype's defaults gets overwritten.