Adding watch flag for folders.
Reformatting NotificationManager.
Making notifier an Akka actor.
Removing implementation-specific types for EventManager.
Removing collection of events into single notification.

Allows polling to be removed and replaced with triggering.
Fixing notificationJson test.
WIP: Refactoring NotifierImpl in preparation to remove polling.
Switching notifications from event-triggered polling to pure evented.
Refactoring away now-unnecessary notifications code.
Simplifying NotifierImpl and its templates.
Adding test to establish watching folders works.

This functionality appears to have been implemented much earlier, but a test for it wasn't created.
Deduplicating notifications for multiple applicable watches.
Improving event manager logging messages.
Merge branch 'watch-folders'. Resolves #65.