Warp documentation

Adding more documentation and tests for *Warper* and *ProjectorFramePacker*.  

(In retrospect, it would have been nice to have the class names match the file names.)

I added .rst files for each class and verified each gets added to the documentation index after building, but I didn't know the best way to further integrate into the documentation so I'm leaving that to someone else.

Also added a sample warp file.