Convenient Methods for Accessing the World Directly Through `&World`

[zicklag]

Right now the only ergonomic way to modify the world is through systems, which take component and resource parameters. This results in a large number of function parameters, which, while helpful for multi-threaded system scheduling later, isn't needed in all cases and is potentially annoying.

There are also times where you want to be able to modify the world more easily outside of a system.

What we want to do is create an ergonomic way to access and modify the world directly on the &World, without having to create or run systems to do it. This will help in situations where you want to just take a &World parameter in a system, and when you want to modify the world outside of a system.