Toolbar Button and Menu Slots

[DonQuarther]

I created a multi-line menu that displayed items and gave them upon clicking. Then, I added a toolbar. An item from the toolbar that was in slot 0 (on the toolbar) had the click properties of an item located on the next page in slot 0. Please fix this.

So far, I haven't found any bugs, but I have more to add.

1. Add the ability to choose the type of inventory so that it can be set to not only 9 * (number of rows).
2. Add automatic row calculation to avoid extra rows. I think this would be convenient and very useful for someone. It would eliminate the need to specify rows in the constructor.