Add list command for AggregateCounter
  Added list REST endpoint at AggregateCountersController
  Made AggregateCount implement Metric
  Updated XDShell command API for list
Fix delete operation for AggregateCounterRepository
  Fixed deleting aggregatecounter's metric meta 'set' when deleting it.
Fix review comments
  Fixed AggregateCount not to implement Metric
  Added tests for aggregatecounter list, delete
  Added AbstractMetricIntegrationTest abstract class for metric helper methods
  Updated other shell tests with the changes
XD-619 Add list command for AggregateCounter
XD-620 Refactor test cases to move away from inheritance model of utility methods for streams, counters
Introduce String.format() style parameters to test utility methods
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
XD-592: Add @Ignore'd tests that showcase the problem