Pipeline-dp

- Adding mean in DataFrame API
- Improvements in Utility analysis

Added possibility to group by multiple columns in DataFrame API

Pre-release with minor fixes. "rc" in the version was removed, since Google Dataproc supports only versions x.y.z

Fixed folder structure

1. Many improvements.
2. Dependency on the new RC version of PyDP, which built with Manylinux images (so it's more portable)

v0.2.1rc5b
Remove dp_accounting dependency

v0.2.1rc5a
Remove dp_accounting dependency

Remove dp_accounting dependency