All barracks building added

- All of the barracks buildings are now usable. Using the 64px texture.
- Created the prefabs, JSON, factory.
- Fixed bug with unit production overlay, which caused a flicker because
it starts are 0,0,0 position.
- Added a notification when trying to buy a unit and you dont have
enough gold.
- Edited level one so it has all of the barracks for testing.