Rename pkgdb2 into pkgdb2client

This prevents the conflict with the pkgdb2 module provided by the pkgdb2
server.
Rename the `pkgdb` logger into `pkgdb2client` to be consistent with the module name
Adjust import and logger in pkgdb2_cli for the `pkgdb2client` change
Adjust the setup.py to include `pkgdb2client` instead of `pkgdb2`
Merge pull request #3 from fedora-infra/rename

Rename