Integrate skimage ORB detector/descriptor

[Purg]

This would add the ability to use the full stack without license concerns of the colorDescriptor software.

[Purg]

http://scikit-image.org/docs/dev/api/skimage.feature.html#orb

[Purg]

No longer especially really relevant algorithmically given deep learning. The relevancy of being able to use a descriptor generator without additional non-pip-installable dependencies is still there, however.