add a Gauge for heap off memory usage

git-svn-id: https://svn.apache.org/repos/asf/incubator/sirona/trunk@1540615 13f79535-47bb-0310-9956-ffa450edef68
reverse properties order loading System props win/override

git-svn-id: https://svn.apache.org/repos/asf/incubator/sirona/trunk@1540616 13f79535-47bb-0310-9956-ffa450edef68