Make it possible to create a CustomTabsIntent, where the package name is set.

[hnljp]

At the moment we use getAuthorizationRequestIntent() for login in and createCustomTabsIntentBuilder to create an intent used to log out.
The problem is that AppAuth is at the moment not supporting the default browser, so the intent returned by getAuthorizationRequestIntent() is using a browser that is possibly not the default browser, but the intent created by createCustomTabsIntentBuilder().build() is using the default browser.
That problem is being worked on with #379 but it would be nice, if you choose a BrowserDiscriptor when setting up the AuthorizationService, that it would also be respected by the log out intent.
This is most likely related to #366