Demos big update

-Added some more math functions
-fixed many memory leaks
-added AABB and BVHTree support to collision.d
 *BVHTree has only incrementally adding entities implemented by now (and bad BottomUp algorithm)
 *ECS Systems use two trees, one for static and one for dynamic entities, dynamic BVH is builded every frame from scratch by now
-BrickBreaker now uses BVHTree to collision detection
 *balls only use tree for checks (they aren't adding to tree)
-fixed bug leading to crash

demos/utils/source/ecs_utils/math/vector.d

@@ -44,6 +44,11 @@ struct vec2
         else static assert(0, "Operator "~op~" not implemented");
     }
 
+    vec2 opUnary(string op)()if (op == "-")
+    {
+        return vec2(-x,-y);
+    }
+
     ivec2 opCast()
     {
         return ivec2(cast(int)x,cast(int)y);