Adding Color to pieces (#31)

Just adding a color field to pieces for drawing later

Carefull when you review, I also moved Vec2 to Utils where I feel it belong.

Solve #29

Co-authored-by: Anthony Debucquoy <debucquoy.anthony@gmail.com>
Reviewed-on: #31
Reviewed-by: Mat_02 <diletomatteo@gmail.com>

app/src/test/java/school_project/PieceTest.java

@@ -36,7 +36,7 @@ class PieceTest {
                 {true, false, true},
         };
 
-        Piece piece1 = new Piece();
+        Piece piece1 = new Piece(piece2_matrix);
         piece1.setShape(piece1_matrix);
 
         Piece piece2 = new Piece(piece2_matrix);