Bugfix and Improvements
emqttd#781: Update README for EMQ 2.0
emq_dashboard#84: Show the Cluster Status of Node
emq_dashboard#79: disc_copies to store mqtt_admin table
emq_auth_clientid: disc_copies to store mqtt_auth_clientid table
emq_auth_username: disc_copies to store mqtt_auth_username table
emq_mod_subscription#3: Remove emq_mod_subscription table and module.subscription.backend config
emq_plugin_template#5: Unregister Auth/ACL modules when the plugin unloaded