redo BITAuthenticator interface

given the good feedback we got, this is take 2
of the BITAuthenticator interface.
It's simplified, cleaned up and now allows full
control over the authentication process.
Major changes:
* manual mode
  Authenticator provides the bits to show the
  viewController to identify the user as well as to
  trigger validation on behalf of the developer.
* process separation
  identification and app-usage-restriction are now
  2 completely separated things.
* public identifier
  Authenticator now allows the developer to query
  parts of the information, e.g. the UDID or the user's
  emailaddy once identified
update needsValidation

return YES even if already validated but
there's a version mismatch.