Edit button now redirects to edit wp instead of show.

https://www.openproject.org/work_packages/15151
@myabc redirect_back_or_default unescapes and then escapes back_url which causes problems when the url contains '='. i spent a while trying to get it to play nicely but so far couldn't find a way of coercing it into giving something back that the browser accepts and also is something parsable by the front end.