Remove controller serializers

This feature is currently only in the dev master branch. After some use Ive found that serializers (at least how theyre implemented right now) dont anything of value and I'd like to remove this feature before the feature freeze before we break existing apps depending on this

Basically all this does can be done by doing 

    return MySerializer->serialize($whatever);

inside your controller, no need to add a seperate hook

@DeepDiver1975 @MorrisJobke @LEDfan