Move complex logic to entity managers

All game code will be splitted into three concepts:
1. Data classes (shared) with constraints. No complex logic
2. Managers deal with complex logic
3. Type-objects used to describe entity. It can be easly serialized/deserialized in Godot Resource format and JSON

## Tasks
- [x] Rewrite base classes -- remove complex logic
- [ ] Write singletone managers to manage/handle entity data class
- [ ] Keep already written type-objects