allow to unregister registered "on complete" callbacks

[patriciagarcia]

Both locationsService and productsService provide a callOnReplicationComplete function. While that function was created to be used by other angular-nav-data services (lgasService, statesService, zonesService and productsListService) and it works fine for those, since it's publicly available it could also be used by components within the app including angular-nav-data as a dependency. Since components are created and destroyed all the time, in order to have the right component registered to an event without going over the limit of the EventEmitter is to register to the event $onInit and unregister $onDestroy, for that a function for unregistering callbacks is required.