Need to reshuffle directory so tests can be run.

Todo:
- Add templates for common states.
- Tests.
- Documentation.
- Look into using a std::deque or maybe std::map (with an ID system) instead of std::vector.
- Timing system that on every update, the back might be deleted if old.
- std::shared_ptr for pointer to engine type for safety.
- Make states std::unique_ptr's for safety.
- Look into reference use.
- Design variable parsing with va-args templates and tuples.
- Using references over pointers maybe.
- Look at using curiously recurring template pattern (CRTP) maybe.

Added doc comments to the files:
- engine.hpp
- base.hpp
- basic.hpp

Fixed shared data. Use <global-data-class-name>::instance()-><member/method>

Next stage is to redo README and documentation