fix wrong entity for channel product creation
refactor method addGcProductId  for better naming
add logging and comments
fix bug which avoided to save flag_code
make product attribute undeletable
refactored product creation
added helper methods to get property set ids and company product IDs
fixed bug in exception throwing, so the exception is caught
removed todo, I think this isn't doable better
add comments
for creating products, we only want virtual and simples
refactored variable names and added comments
add a helper method to determine wether a product is physical
get correct language from store for created description
check whether product price is incl or excl tax
add packaging unit
get property set for correct store