Removed refresh, added resourceChangeListener

The resource change listener listens for changes done in
the createrepo project. Currently, it modifies the preferences if
an RPM in the project is removed and is also still in the properties.

TODO: decouple the listener/delta and the formpage if possible
    o make the listener/delta handle import events as well to change
      the preferences if a new file is added to the project

Signed-off-by: Neil Guzman <nguzman@redhat.com>