Capture Color

[UE] Add a tutorial of application to show the users how to use this application.
[UE] Improved user experience of composing color tubes from droplets.
[UE] Use can directly capture for more droplets on the capture result screen.
[BUG] fix a bug of synchronizing paintings after user signs in back.
Modal window for on-screen guides, so that users cannot miss them with unintentional touches.
Change default behavior of Terms of Use Dialog shown when user sign in this application.