support list conference (#321)

* support list conference

* add test case

* fix conference action requires tag

* fix failing test case

package.json

@@ -28,7 +28,7 @@
     "@jambonz/db-helpers": "^0.9.3",
     "@jambonz/lamejs": "^1.2.2",
     "@jambonz/mw-registrar": "^0.2.7",
-    "@jambonz/realtimedb-helpers": "^0.8.8",
+    "@jambonz/realtimedb-helpers": "^0.8.9",
     "@jambonz/speech-utils": "^0.1.0",
     "@jambonz/time-series": "^0.2.8",
     "@jambonz/verb-specifications": "^0.0.69",