Add scoreboard score calculation

[martinreinok]

This could be fun if it was score which is a function of time, so when player(s) is(are) able to multitask and place Tetrominos very fast, they can get a multiplier.

• Function of time score can be implemented as a bonus score to every block. When a new block is dropped, a timer starts (probably a new thread), and based on that time player can earn some bonus points e.g. bonusPoints = min(100 - timeElapsed^2, 0)

Other than that, basic tetris score; single line double line triple line quadruple line

[MennoScholten]

Implemented a solution sort of similar to original tetris. By taking a shortcut and using the equation prevScore + 6^amountoflinescleared it will create a score which is similar to the original function in the sense that the score is increasing a lot when a lot of lines are cleared at once.