DebugTools: render also non-axis-aligned boxes with proper size.

Yay for this convoluted mess (but hey, it's generic code working for
both 2D and 3D!).

src/DebugTools/Implementation/BoxRenderer.cpp

@@ -24,7 +24,8 @@
 namespace Magnum { namespace DebugTools { namespace Implementation {
 
 template<std::uint8_t dimensions> void BoxRenderer<dimensions>::draw(Resource<ShapeRendererOptions>& options, const typename DimensionTraits<dimensions>::MatrixType&, typename SceneGraph::AbstractCamera<dimensions>* camera) {
-    this->shader->setTransformationProjectionMatrix(camera->projectionMatrix()*camera->cameraMatrix()*box.transformedTransformation())
+    this->shader->setTransformationProjectionMatrix(camera->projectionMatrix()*camera->cameraMatrix()*box.transformedTransformation()*
+        DimensionTraits<dimensions>::MatrixType::scaling(typename DimensionTraits<dimensions>::VectorType(0.5f)))
         ->setColor(options->color())
         ->use();
     this->mesh->draw();