Change the overall interaction with ECS

[Timofffee]

The current implementation is too straightforward and verbose. I think it's worth putting the systems into separate "classes" (as far as possible), and simplify the addition of components (if you need an entity with one component, there's no point writing extra code).

For example:
https://github.com/Leopotam/ecs#custom-engine

[Timofffee]

After studying the work of some ECS, I came to understand that the easiest way to store systems is in classes that will have methods Init(), Update(), LateUpdate() and so on.

Plus, the systems can be stored in the world itself. Also, with this approach, it will be easy to implement caching of components for each system separately. The only problem I don't know how to solve yet is how to update the caches?