Introduce touch down event support for CCMenu

[giginet]

We can't activate callback functions when MenuItems are pressed down.

This PR make it to enable to handle touch down event on Menu.

auto menuItem = cocos2d::MenuItemImage::create("button.png", "button.png", [](Ref *button) {
    cocos2d::log("touch down event");
});
auto menu = cocos2d::Menu::create(menuItem, nullptr);
menu->setEventType(cocos2d::Menu::EventType::TOUCH_DOWN);

[pandamicro]

I think it's a good add-up to the current Menu system, but it adds new APIs, so I need your opinion @minggo @zilongshanren

[giginet]

Hi, any update on this issue?
do you think about this feature? Please check it.
@minggo @zilongshanren

Thank you 😃

[minggo]

Why need these codes?

[giginet]

Because if event_type was TOUCH_UP, activate should not be called when touch is began.

[minggo]

There is already onTouchBegan, onTouchMove events, why need these events? And it seems they are duplicated.