Allow to retire on Fedora collections that are 'Under Development'

This would allow user to retire on a branched collection as long as its
status has not been set to 'Active'.

Fixes https://github.com/fedora-infra/pkgdb2/issues/81
Release 1.18.1 and adjust documentation accordingly
Add unit-test testing the behavior if the user retires a package on a branch that does not exist
Update update_pkg_status to handle the situation where the package does not exists on the specified collection
Add unit-tests to retire package specifically on EPEL branches
Add unit-tests checking if we can retire an orphaned package via the API
The EPEL collections are actually named Fedora EPEL, expecting something else won't work
Adjust the unit-tests so that we are consistent is the naming of EPEL collections
Release 1.18.2 and adjust documentation accordingly
If the user is a group, use the group's mailing list as email for bugzilla
Import the latest pkgdb-sync-bugzilla script from the infra repo
Adjust the setup.py script to install pkgdb-sync-bugzilla in /usr/bin
Make pkgdb-sync-bugzilla rely on the configuration file from pkgdb2
Add settings specific/used by the ``pkgdb-sync-bugzilla`` script in the default configuration
Include SITE_ROOT and SITE_URL in the default configuration
Update the sample configuration file

This changes include the new configuration key:
SITE_ROOT and SITE_URL which provide information as to where the application
is deployed
PKGDB2_BUGZILLA_NOTIFY_EMAIL and BUGZILLA_COMPONENT_API used by the
pkgdb-sync-bugzilla script to sync package information from pkgdb to
bugzilla
Move the pkgdb-sync-bugzilla from getopt to argparse
Add a PKGDB2_BUGZILLA_DRY_RUN configuration key to specify in the pkgdb-sync-bugzilla script runs for real or not
Adjust the DRY_RUN flag in pkgdb-sync-bugzilla

The flag now relies on the configuration file or the cli argument to
debug the script
Add a little more debugging when running with --debug