Sales management

This is the sale management function. 

Currently, sales are only working for all attributes only, not on specific attributes. For example, it we have a tee shirt in red, blue and green, it is not yet possible to offer a sale only on the red one.

True. 

This is also true for a bunch of other loops, and numerous parts of the code where the class namespace was used (why ?) insdead of importing it.