Completely restructured code, entities are split up into components, added JSDoc definitions, general cleanup

[Lizzaran]

Changes:

• Restructured code, mostly for entities
• Entities are split into components
• Communication between entities/components are done via singleton mediator class
• Added JSDoc annotations to have at least some sort of type hinting
• General code cleanup
• Added some small features like zIndex, "durability"/uses for items, functionality that entities can walk on other entities