SLING-3485 : Expose JSON Servlet Helpers

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1612841 13f79535-47bb-0310-9956-ffa450edef68
SLING-3485 : Expose JSON Servlet Helpers

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1612842 13f79535-47bb-0310-9956-ffa450edef68