Ranker options

Remove the boatload of arguments passed to `QSDefaultRanker` and pass them in an `NSDictionary` instead. I've tried to keep compatibility with other rankers (TextStart anyone ?) but didn't really test thoroughly (I'll try it and add commits if that's the case). Be aware that until the others rankers get updated, they will happily ignore unknown options.

Please consider that I did that because calling through `[[NSUserDefault standardUserDefaults] boolForKey:@"QSUsePureStringRanking"]` *each time* you'd be ranking something was apparent in an Instrument run I did to find out why the hell the result list took so long to keyboard through (both from the direct pane and the action pane).

My finding point out this thing as one culprit, the other being animating the interface when there's a indirect pane to show. But that's for another pull req ;-).