drive3 API for Drive v3 API

src/gam.py

@@ -673,6 +673,8 @@ def getAPIVersion(api):
   version = API_VER_MAPPING.get(api, u'v1')
   if api in [u'directory', u'reports', u'datatransfer']:
     api = u'admin'
+  elif api == u'drive3':
+    api = u'drive'
   return (api, version, u'{0}-{1}'.format(api, version))
 
 def readDiscoveryFile(api_version):

src/var.py

@@ -91,6 +91,7 @@ API_VER_MAPPING = {
   u'datatransfer': u'datatransfer_v1',
   u'directory': u'directory_v1',
   u'drive': u'v2',
+  u'drive3': u'v3',
   u'email-settings': u'v2',
   u'gmail': u'v1',
   u'groupssettings': u'v1',