Re-factored ElementAccesor.perform to return Response and make getNodeById use it.
Renamed json package to model.
Removed unused code.
Removed now unused getRootNode method.
Introduced perform method to factor out common code.
Cosmetic changes.
Properly pass given data to perform.
Re-wrote getting elements via their path using the new architecture.
Introduced NodeAccessor inner class to retrieve a node from its id or path.
Removed path parsing code since it's not needed anymore.