Skill Games improvements: Demo mode and Bombermad Gamepad

[Admins]

We have improved several aspects of the skill games server:

- Fixed a problem with the computer player not doing anything when being in check, but not check-mate
- BomberMad can now be played with joystick or gamepad
- Most multiplayer games have a demo-mode, click the button next to the Restart-button to enable it. You will see computer players playing against each other, endlessly.