Additional doc for defMetric
Additional doc for defMetric

refs #1191

phelipealves/omf,LABORA-UFG/omf,mytestbed/omf,mytestbed/omf,LABORA-UFG/omf,mytestbed/omf,LABORA-UFG/omf,ardadouk/omf6,ardadouk/omf6,mytestbed/omf,phelipealves/omf,LABORA-UFG/omf,phelipealves/omf,phelipealves/omf