Notifications System core

Following https://issues.cask.co/browse/CDAP-849 jira and design doc.
Build is running at https://builds.cask.co/browse/CDAP-DUT320-3.
In Standalone, everything is running within the same JVM, what's the point for making HTTP call? As we discussed before, the notification http handler is just a bridge to the feed manager to do the actual work. So in standalone, why can't it be done by just calling the feed manager directly but instead have to go through HTTP? What benefits do we get?