Alert e-mails are shown in HTML

It should be possible to enter plain text (or formatted text) when configuring alert e-mails. Both default and alert-specific.

I don't think users will like to write HTML as mail body.

Solution: It should be possible to edit the mail body and subject as HTML or as formatted text (WYSIWYG editor). Perhaps could there be a fan for each option - concrete solution can depend on what is easiest to implement.