Add a mean to collect and show the Requests Events durations using Metrics  https://issues.apache.org/jira/browse/OFBIZ-5198
Fulfill the goal with some more:
* makes the Metrics main parameters (estimationSize, estimationTime and smoothing) dynamically changeable (added in serverstats.properties)
* there is no threshold handling for event metrics


git-svn-id: https://svn.apache.org/repos/asf/ofbiz/trunk@1485601 13f79535-47bb-0310-9956-ffa450edef68