QuestionFragment: save the classification in an AsyncTask.

This reduces the amount of work happening on the main UI thread.
StrictMode complains about this at least on API 15 and API 16 target
devices.
LoginActivity: Do the account addition in an AsyncTask.

Because StrictMode complains about this at least on API 15 and
API 16 targets.
QuestionFragment: Avoid responding to "Done" twice.

In theory, a user could press the Done button again while we are saving the
classification.