Add the pdc_modules toddler
    
    This toddler reacts on state change message coming from MBS and either
    updates or create a new module in PDC.
    
    This toddler is the equivalent to the pdc-updater handlers:
    https://github.com/fedora-infra/pdc-updater/blob/develop/pdcupdater/handlers/modules.py
    
    Signed-off-by: Michal Konečný <mkonecny@redhat.com>