MainActivity should change mode to card mode when a card is presented

When the MainActivity is started and a card is presented it should change the OTP icon to showing the icon of the SP (either Fidesmo or Yubico). The back button should also return one from the card mode to the phone mode where tokens are stored internally. This might be achieved by restarting the activity with the PendingIntent in the other mode. Some parts of this is already started, with some of the other activities accepting an "internal" boolean as part of their intent bundle to indicate the mode.