Added bindings for healing
some Bugfixes

- Corrected random drop chances
- Some sounds are played multiple times
Changed include direcory format.

Original: #include "../file.h"
New: #include "src/file.h"
Reordered file structure
Removed ItemReference.

In the old version, there was a class ItemReference that made it possible to refer to items before they are loaded.
The new version loads them as soon as they are used.
This makes code shorter, removes memory usage and makes future improvements easier.