Add a typedef for the CustomReceiverProducer function

Add a typedef for the CustomReceiverProducer function
Modify CfgParseParams.CustomReceiverProducers to use this typedf
Add a funtion that creates a new initialized instance of CfgParseParams

GitHub support seems to be week when sending a pull request for another branch than master
or maybe I did something wrong ...
I hope this works or that you at least can see what I added.