Subproducts now may use parent sale instead of their own.
Parent sale migration, the subproduct attribute used to be a proxy, so a new table is created.
Missing imports, invalid argument, wrong calculation and a superfluous comma.
Translation of the new field strings.
Missing attribute options' translations.
Resolved wrong CharactersValue calculation when used as a subproduct of a product with a sale.
PEP8: Unnecessary import and a blank line.