Clean up colorContours directory

1) remove hh folder
2) merge files under folder dhb and folder dhb/colorContour
3) remove dhb/colorContours/validation (updated ones are in
frontend/validation)
4) remove ellipse (they are in frontend/external)
5) remove receptors folder (updated ones are in isetbio)
6) remove some unused code (coneSamples, etc.)
Merge pull request #4 from isetbio/HJ

Clean up colorContours directory

I looked this over and it seems like a good step in the right direction.  I pushed some buttons on the gitHub page which I think will merge it into the master branch.

David