new profiling wiki page

We need to add a wiki page that is updated every tagged release with performance data. Someone must be assigned to maintain this wiki page.

it should show FPS/SSIM numbers for 4k, 1080p, 720p clips at many presets on quad-core desktop and a server platform.

The wiki is a Mercurial repository, so updates to this page could be completely automated. One just needs to learn Markdown or Creole and write the appropriate scripts.