Update cell line data to use orcestra-downloader

[sgosline]

There is a python-based way to access the cell line drug data here: https://github.com/bhklab/orcestra-downloader

This could help address the reduction in image size for #230 .

[jjacobson95]

Just a note - I looked into this package and all of the files are downloaded as RDS files. We can use pyreadr in python to load these in directly as pandas dataframes without needing R installed. This would be a pretty significant overhaul of the current code we use to download our cell lines but certainly doable.

NCI60 is included as well, so this could be joined in directly rather than a separate step.