XD-549 Add 'display' command for RichGauge
     - Display string representation of richgauge metric values
    (example: name: r1, value: 15.0, avg: 12.5, max: 15.0, min: 10.0)
  Added richgauge tests
     - Added AbstractMetricIntegrationTest that has metric specific helper methods
     - Fixed tests that use metric methods
Fix review comments
 - Added RichGaugeResource domain object to include alpha and count
 - Replace RichGaugeOperations' method name display to retrieve and to return RichGaugeResource
 - Added RichGaugeResource's display command to return Table
 - Added pattern option to format metric values
 - Added tests for RichGauge display, list and delete commands