FPSCounter: Flush the logs every second and close them when the renderer is shut down.

We also move `FPSCounter::Update()` to RenderBase, where it is called after `SwapImpl()`, does this affect our results?
Maybe you want to expand it with more logging information? I normally reserve final for situations where inheriting the class would have unintended consequences.

If you think it should be final I'll make it final though.