gam usage and gam usageparameters commands

usageparameters prints the parameters reported for customer and user
usage. usage generates a CSV of specified parameters over a given date
range. From a Google Sheet it's useful to add a chart to get a nice
graph showing changes in G Suite service usage by users over time.

src/gam.py

@@ -11236,6 +11236,12 @@ def ProcessGAMCommand(args):
     elif command == 'report':
       gapi.reports.showReport()
       sys.exit(0)
+    elif command == 'usage':
+      gapi.reports.showUsage()
+      sys.exit(0)
+    elif command == 'usageparameters':
+      gapi.reports.showUsageParameters()
+      sys.exit(0)
     elif command == 'whatis':
       doWhatIs()
       sys.exit(0)