Refactoring parent app delegate out of native apps

This is the first pass at the refactoring of the native code to no longer require the use of a parent app delegate.  This most significantly involved the refactoring of `SFAuthenticationManager`, to truly manage all of the authentication flow, passcode functionality, secure screenshots, etc., that were happening in the parent app delegate.

RestAPIExplorer's `AppDelegate` shows the updated pattern that will ultimately be used for the new template app.