Allow people to assign class properties without automatically generating a class for each element

So I figured out that MCreator currently generates a new .class entry for every element in the world space. This ends up bloating the size of mods unnecessarily. A good workaround would be to let us choose whether to assign a new element to an existing class or generate a fresh one. That way, we can avoid duplicate class files and keep mods lighter and with better performance - smaller files need less Ram to load resulting in better frames for potato pcs.

Another thing I’d like to suggest: since layers already exist, it would be amazing if we could assign animations to them or group them with existing animation bones for models and the item display feature. I actually have some code that does this (though it might need cleanup, since I’m not the best at coding), and I’d be happy to share it if you’re interested.

Finally, I’d also love to provide some built-in models and animations so people can build more stuff with less effort.