* animation renamed to sprite
* renderable/surface renamed to texture
* added in d2math: Vector2, Vector3, Vector4, Matrix3, Matrix4, Quaternion
* worked a bit on the loading scene, main menu scene
* added `d2common/d2input`, copied input vector logic from hellspawner
* added an `InteractiveComponent` which contains input vector, enable
flag, and callback function
* Added an InputSystem which handles input logic and iterates over
entities with interactive components
* added a mouse cursor scene for rendering the mouse cursor
* made the trademark sprite disappear when left mouse is clicked
* various other small bugfixes in scene systems
