Fix bug #1, still sometimes onDateSelected is called twice.

Removed all workarounds except for the one in setShowNumbersInView.
Catch selecting same date twice in parent view.

Anybody who wants to use the DateSpinner or TimeSpinner without the ReminderDatePicker parent will have to apply this patch to the activity (or to their own Spinner).
This is not implemented everywhere for performance reasons (getSelectedDate isn't the fastest method in the world).