Merge the game to dengine, reduce header coupling

Until engine architecture can clearly be separated from the game, i.e.
notion of entity storage belonging to game and concept of entity belonging
to engine, worlds/scenes belonging to game or engine- the project will
only refer to Dengine.

src/AssetManager.c

@@ -21,6 +21,8 @@
 #include "Dengine/OpenGL.h"
 #include "Dengine/Platform.h"
 
+// TODO(doyle): Switch to hash based lookup
+// TODO(doyle): Use pointers, so we can forward declare all assets?
 AudioVorbis *asset_getVorbis(AssetManager *assetManager,
                              const enum AudioList type)
 {