define color map for generated polyominoes

[Raffaello]

mapping the polyonimoes generated, (index based?) or in the file next to the M value, the number to identify the color.

review later when it is required to draw them and have multiple possible polyominoes and customizable colors.

[Raffaello]

• each piece should be represent by 1 root color and 1 brigther and other 2 darkers for a total of 4 (nearby) colors for polyomino.

• the colormap can be defined as index -> root Color eg:

1 => Color.Red
2 => Color.Green
3 => Color.Yellow

the rappresentation of the color in the game grid is the values of those indexing.

To do after the logic represenation of the game: https://github.com/Raffaello/open-tetris/issues/12