Demos update (SpaceInvaders demo)

-added new sprites
-added new functions to vectors
-fixed rendering rotated sprites
-small performance improvement and some bug fixes
-added animations support
-bullets get initial velocity from parent
-added partiles for fire from gun and explosion of enemies

demos/source/demos/snake.d

@@ -285,7 +285,7 @@ struct ParticleSystem
     {
         uint length;
         @readonly Entity[] entities;
-        @readonly CParticle[] particle;
+        CParticle[] particle;
     }
 
     void onUpdate(EntitiesData data)