Add info for  Kapua REST API to the README
Add info for  Kapua REST API to the README

kartben/eclipseiot-testbed-assettracking-cloud,kartben/summit2017,kartben/summit2017,redhat-iot/summit2017,kartben/summit2017,redhat-iot/summit2017,kartben/summit2017,redhat-iot/summit2017,redhat-iot/summit2017,kartben/eclipseiot-testbed-assettracking-cloud,kartben/eclipseiot-testbed-assettracking-cloud,kartben/eclipseiot-testbed-assettracking-cloud