Use notifications for login failures

* For now, clicking on the notification takes the user to the
  Welcome activity, as we don't have final flows for the new
  account setup UI
* Need comment on strings; the problem is that notification
  text must be rather short if we're to use the standard
  notification display.  It looks like newer UI will allow
  3 lines instead of 2, however.
* Tested w/ IMAP, POP3, EAS, and SMTP

Bug: 2322253
Change-Id: I7ed6fa5599179870cbcdb14af062e956eff37ec5
3 files changed