Fixed the duplicate slots view.
The script would not clear the screen upon recalculation also the list of duplicates would increase with every iteration because the variables weren't properly reset.
Patch by: Merio Ferraro, Lennard de Rijk
Reviewed by: to-be-reviewed
"""Multi-consumer multi-producer dispatching mechanism
Originally based on pydispatch (BSD) http://pypi.python.org/pypi/PyDispatcher/2.0.1
See license.txt for original license.
Heavily modified for Django's purposes.
"""
from django.dispatch.dispatcher import Signal