NoteActionObserverManager

interface NoteActionObserverManager

Observer manager

notifyObserver	Notifies all observers about update `abstract fun notifyObserver(): Unit`
registerObserver	Registers observer `abstract fun registerObserver(observer: NoteActionObserver): Unit`
removeObserver	Removes observer `abstract fun removeObserver(observer: NoteActionObserver): Unit`

This class parses some of actions that can be done with Notes Such as: ADD, REMOVE, SHOW

class NoteActionManager : NoteActionObserverManager