Scenegraph benchmark

WIP: This PR adds a benchmark example for comparing scenegraph performance to similar optimal implementations. 

The intent is to add more benchmark examples and optimizations until we get comparable performance (or decide that we will never get comparable performance).
> Is the #line 2 actually necessary? The test now passes for me.

Really? On my system the wrong line was reported. Can you try to change it and see if it still works?