- Fragment shader: it keeps rendering green fragments until I implement textures.
- Vertex shader: Now a MVP matrix is used.
- Virtual method Drawable:::draw() now takes a projection matrix as an argument.
- Class "Tileset" renamed to "Sprite".
- Struct "TilesetData" renamed to "SpriteData".
- Created static attribute Sprite::vao which keeps the index of a VAO used for rendering sprites.
- Added OpenGL initializations such as viewport and projection matrix initializations.
- As a test, a sprite's "wireframe" is rendered in game's main loop.