Uses new streaming JSON FUELINST source
DHD20240212: broke out FileUtils from DataUtils.
DHD20240212: added json-20240205.jar (org.json, public domain).
DHD20240215: now fetches from new FUELINST JSON streaming API.
DHD20240215: have rationalised cacheing etc somewhat; needs tidy-up of doTrafficLights().
DHD20240215: fetches only as much data as needed (not usually full 24h).
DHD20240215: changed recent data fetch to max of 48h (from 24h).