Define PPLocationManager's public interface

PPLocationManager is a façade providing access to the
location subsystem. It collects interfaces exposed by
various classes that provide highly specific location related
functionalities and exposes their behaviors via a high
level interface.
Register for app did finish launching notification

PPLocationManager class is currently designed to
instantiate itself when the app is launched. With this
approach we can keep the code in app delegate relatively
clean.
Determine if the app was launched due to location change
Determine if location background mode is enabled