Google Code-in

Add an history of QR Code generated (or read). So the user could retrieve its history when he reopen the activity. The history could be represented by a sort of ComboBox in the input field. The history should be stored in the datastore. See https://github.com/llaske/sugarizer/blob/dev/docs/tutorial_step4.md for more. The source of the QR Code activity is located here: https://github.com/llaske/sugarizer/tree/dev/activities/QRCode.activity