Code reorganization and TCIA summary script

@mehrtash: I wanted to pull information on all the series available in TCIA, so I wrote a small script for that. While I was doing it, I moved TCIAClient to a separate library to facilitate reuse and improve code organization. Going forward, it probably makes sense to keep helper classes in that library instead of the main python script.

I tested with 'make ExperimentalUpload' and verified that the updated extension was installed and functional.

I leave it to you to review and merge, so that you are aware of the changes and in case you spot any problem.