Add basic functionality to draw instances

Allows creation of instances of meshes and drawing all of them with
single draw call. Instances can have their own transformation data
(location, rotation and scale).

graphics/rse_graphics.hpp

@@ -13,7 +13,8 @@ class RseGraphics {
     RseGraphics(const RseGraphics&) = delete;
 
     /**
-     * @brief Initialize graphics module, runs main loop and deinits everything, when interrupted
+     * @brief Initialize graphics module, runs main loop and deinits everything, when interrupted.
+     * This has to been run AFTER all scene objects have been already created.
      *
      * @return uint8_t 0 on success.
      */