bug 889041 - return any raw field from report/list

@rhelmer @AdrianGaudert @selenamarie r?

I would suggest you fetch it down and have a play but it's a bit tricky if you're relying on dev db since the middleware there doesn't include `raw_crash` in the Report. 

Here are some nasty screenshots showing what can happen if you include too many fields :)
http://cl.ly/RaJc
http://cl.ly/Rb0U

I was tempted to implement select2 for the fields but the way it works now actually isn't too bad. It's compact and clear and doesn't require any extra heavy javascript or css.