Make items more generic.

[HexDecimal]

Right now items are setup as an abstract class and use polymorphic subclasses to define behavior. I want to change this so that items are a generic mostly-static type which can point to the behaviors they use. This should make it easier to add and remove item behaviors since right now serialization is a real pain.

Data associated with items should be moved to a dictionary like type. Something like std::unordered_map<std::string, std::any> or something more strict.