CDAP-798 use increment and gauge in mr metrics

Reintroducing Metrics increment in mapreduce metrics writer. and using metrics increment for entries processed , while using gauge for process completion and other metrics. 

Also added type of the metric(counter/gauge) to the MR counter group and using that information to call increment/gauge.

This PR is to fix the issue at : https://issues.cask.co/browse/CDAP-798