replace checkboxes by radio buttons in beat/duration/division type menu

these items behave like radio buttons: clicking on an already checked item
leaves it checked

desktop/TuxGuitar/src/org/herac/tuxguitar/app/view/menu/impl/DivisionMenuItem.java

@@ -34,7 +34,7 @@ public void showItems(){
 
 		for (int i = 0; i < TGDivisionType.DIVISION_TYPES.length; i++) {
 			final int j = i;
-			this.divisionTypeMenuItems[j] = this.divisionMenuItem.getMenu().createCheckItem();
+			this.divisionTypeMenuItems[j] = this.divisionMenuItem.getMenu().createRadioItem();
 			this.divisionTypeMenuItems[j].addSelectionListener(new UISelectionListener() {
 				public void onSelect(UISelectionEvent event) {
 					DivisionMenuItem.this.createDivisionTypeAction(DivisionMenuItem.this.createDivisionType(TGDivisionType.DIVISION_TYPES[j])).process();