Use bundle_id as default server_id

Put server_id (either the SERVER_ID environment variable or the
bundle_id) in the Meteor run time config, where it is used by both
stream_server.js in the welcome message and by stream_client.js to
determine when an update is availabe.

Turn off verbose server logging.
Merge remote-tracking branch 'origin/appcache-experiment' into appcache-experiment