Revision D2 (WorldSlice | Movement | Todo List)

Created Class:
- WorldSlice

Created Notes folder:
- Todo List text file

WorldSlice:
- Represents one vertical slice of the game world.
- Contains array of WorldChunks
- One WorldChunk wide
- X WorldChunks deep

Other:
- Added "Name:" and "Purpose:" comments to the top of all class files.
- Created basic camera movement in Engine class. This is NOT the final
movement system.
Purely for debug purposes. Camera and world classes will be created to
move this functionality out of the Engine class, as it is considered
clutter.