Add dataregistry to desc-python

[stuartmcalpine]

Should we request to add dataregistry to the desc-python environment.

Maybe after beta testing is complete?

[JoanneBogart]

After just now following all the instructions needed to install dataregistry and incorporate it in my own jupyter kernel, I heartily agree that dataregistry belongs in the desc-python environment. This is just too much overhead to subject people to.

I have to say the process, though many steps long, generally went smoothly. The only thing I would change on our doc page http://lsstdesc.org/dataregistry/installation.html would be to suggest that, if you expect to use dregs from jupyter, the conda create line should also include ipykernel