Have _get_active_branch and _get_user_packages use the global pkgdbclient

This prevents querying package information from pkgdb prod while running
pkgdb-cli with --test (ie against staging)
Add support in pkgdb2client in update_package_poc for the former_poc argument
Do not return packages if _get_user_packages was not provided with an username
Adjust the documentation for --poc in pkgdb-cli give to the reality
Add support for the --former-poc argument to pkgdb-cli give
Simplify the code by relying on one former_poc instead of calling argparse all the time
Allow give multiple packages in one go by passing a pattern as package name
Support orphaning packages matching a pattern if a former_poc is specified
Merge pull request #20 from fedora-infra/fix_give

Fix give