Moving Follow code to Core

Moving Follow code to Core. Making it available to other GCSes
what do you mean by notification queue?

For an example of what I suggest, the first line in `enableFollowMe` sends a `FOLLOW_START` event. Based on that, there's no need to have `TextNotificationReceiver` since the front end components (android, desktop, ...) can decide how they want to handle the event (toast message, pop up).

`TextNotificationReceiver` in this case is redundant, and constrained since it only does on thing that's already well covered by the broadcasted events.