S2716 pull request reorganization #1

Improvements to MetricsFilter
I didn't change this MetricsFilter.scala by my decision.
I just took the version of  MetricsFilter.scala from previous PR :
https://github.com/DrillingInfo/metrics-play/commit/9ab316b51bee32f4d5a8d8d4f758fffe4c250911
and put it here.
I'll fix this class, close this PR and create a new one.