Grant default permissions to the setup app robustly.

There is a zoo of components that handle the home intent and
have different priority. There is no reliable way to distinguish
the setup app from the other apps that handle home as some of
them have lower priority than the setup app and some higher.
This change adds a dedicated category to recognize the default
setup app.

Uncommented the code that grants accounts permissions as the
get_accounts permission is now a runtime permission and can be
granted.

bug:22471024
bug:22501463

Change-Id: I41726751fa2567cbcd7d09c7acfa7615b8aba577