Handle back button on ConfigurationWizard
From UI Rev II: “Back” quits when there is no configuration. If we got here by a “Switch provider” menu selection, we leave previously configured provider in place and return to whence we came. Implies “Clear config” option, probably in Preferences (see Preferences section)
-Put an AlertDialog for onBackPressed() that tells the user they must configure the app or quit: configure cancels the dialog, quit clears any already saved config and quits the app-
(from redmine: created on 2013-06-27, closed on 2013-07-04)