[fixes #137] When there are still stones to capture, it now displays a different error message.

Added the "Make sure your board matches the virtual one."-part because when you make any other changes to the board besides capturing stones, the backend still returns UpadateResult::ToCapture.
Merge pull request #143 from augmented-go/#137_capturing_stones_message

[fixes #137] When there are still stones to capture, it now displays a d...