Remove image unwrapping. Replaced by 'forward sampling'

'forward sampling' sounds cool isn't it?

Based on quick tests, detection duration is divided by ~2. Especially useful when many tags (or many rectangles) are present in the image.

While here, added more test images + a sample application that simply takes an image and list all detected markers + fix a nasty bug in Refine.

I should probably split out this pull request. Let me know if you wish so!