Fix LabelCombiner bug and simplify labeling code

Most changes are made in nab/labeler

I also changed from using both yaml (for configs) and json (for labels) to only json which helped simplify a lot of the logic. 


Right, but they would add those in the labeling tool right?  If so, the comments need to be stored in the JSON itself as a field.  I don't think we need to switch to YAML for that.