update clear function in multidoku + solver soolve

app/src/main/java/sudoku/MutableCell.java

@@ -21,13 +21,18 @@ public class MutableCell extends Cell{
 		this.symboleIndex = symboleIndex;
 	}
 
-	public void clear() {
+	/**
+	 * Remove the current symboleIndex and returns it
+	 * @return integer symboleIndex cleared
+	 */
+	public int clear() {
+		int i = this.symboleIndex;
 		setSymboleIndex(NOSYMBOLE);
+		return i;
 	}
 
-	public void clear(int indexSymbol) {
+	public void removeHint(int indexSymbol) {
 		hintsSymbolIndex.remove(indexSymbol);
-		this.clear();
 	}
 
 	public List<Integer> getHints() {