checkIsHostForProgram function takes a new 'logic' argument.
It determines which logic should be used to look up for program entity. If the argument is not given, the standard program_logic will be used.
"""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