Tests with POSIT. Not trivial as it optimises in a different coordinate system.

Note that there's still some problems with solvePnP: The pose estimation
seems quite off for a lot of images.
- Moved helper functions to libRender

- Added (inactive) UpdateStrategy to sdm v2
- Added a ModelFitting class that holds the parameters of a fitting
result
- Modified sdm v2 example towards pose-estimation