#25: Extracted common components of ItemChain and Item classes into ItemMixin. Adjusted Item and ItemChain to inherit from ItemMixin. Extracted common components of AttributeChain and Attribute classes into AttributeMixin. Adjusted Attribute and AttributeChain to inherit from AttributeMixin.
#25: Extracted common components of ItemChain and Item classes into ItemMixin. Adjusted Item and ItemChain to inherit from ItemMixin. Extracted common components of AttributeChain and Attribute classes into AttributeMixin. Adjusted Attribute and AttributeChain to inherit from AttributeMixin.

OOPMan/rightshift