Rekognition Face Detection: change JSON flattening to a set of valueHandlers to create TopicMap data according to response data format

Instead of creating simple occurrence data with flattened JSON keys as keys, use valueHandlers to create occurrance data, coordinates or confidence associations depending on the resposnse datum format. Simple numeric values are represented as occurrence data, JSON object in the form {"x":...,"y":...} are interpreted as coordinates and JSON objects in the form {<String>:<double>,<String:<double>,...} as confidences.

TODO: handle boundingbox and pose.