Finish task A.4. Adde alerting system demo.

Signed-off-by: Haochen Xie <haochen@xie.name>
Persistent storage.

Signed-off-by: Haochen Xie <haochen@xie.name>
Consume clicks.

Signed-off-by: Haochen Xie <haochen@xie.name>
Add map integration demo.

Signed-off-by: Haochen Xie <haochen@xie.name>
Add geolocation demo.

Signed-off-by: Haochen Xie <haochen@xie.name>
Add logo.

Signed-off-by: Haochen Xie <haochen@xie.name>
Add to GPSScreen.

Signed-off-by: Haochen Xie <haochen@xie.name>
Update the way providing buttons on the main screen.

Signed-off-by: Haochen Xie <haochen@xie.name>