refactor: remove unused classes and methods, improve code clarity

app/src/main/java/sudoku/Bloc.java

@@ -18,23 +18,10 @@ public class Bloc {
         cases.add(c);
     }
 
-    public boolean contains(Symbole s) {
-        for (Case c : cases) {
-            if (c.getSymbole().equals(s)) {
-                return true;
-            }
-        }
-        return false;
-    }
-
     public String getCouleur() {
         return couleur;
     }
 
-    public int getCouleurIndex() {
-        return couleurIndex;
-    }
-
     public List<Case> getCases() {
         return cases;
     }