Bug 875401 - Part 1: add JSON utils to HealthReportUtils.
Bug 875401 - Part 2: switch HealthReportGenerator to use org.json.JSONObject/JSONArray.
Bug 875401 - Part 3: refactor out array accumulation, rather than doing it by hand.
Bug 875401 - Switch HealthReportGenerator to use org.json.JSONObject/JSONArray. r=nalexander