Ilsgateway integration

@czue I moved changes from ilsgateway-products-integration to this branch and I added webusers integration. I will be pushing all integrations with ilsgateway in this branch.  Is it ok? I assume that you don't want to merge this changes until it will be completely done?
@czue I'm not sure about this solution. Maybe it's better to add new handler in settings.py instead of sending signal?