Edit button now redirects to edit wp instead of show.

https://www.openproject.org/work_packages/15151
@myabc to be more specific (and just to think out loud) - in order to get rails to be happy with params like '=' they have to be escaped client side. but then when this gets unescaped and escaped it comes back out as '=' instead of '%3d' so when that gets give back to the browser every after the '=' disappears. on the other hand if we don't (un)escape back_url then it cannot get parsed by URI.parse and the default url is returned.

if you can think of something clever to do here let me know. otherwise i suggest just using the alternative that i wrote.