cloudconnector: onedrive replaces skydrive

* OneDrive is the new name of the service previously known as SkyDrive:
  https://github.com/mk-fg/python-onedrive/commit/a69252e

* Deleting PIL since Pillow replaced it.

**NB:** `python-onedrive` is written with python 2.7 in mind (`{set}`, `argparse`, ...)