Issue #2323775 Define data_tables for our translatable entities

- Rename the language field on the product entity from language to langcode
- Define a data_table for our translatable entities, this is enforced now because of https://www.drupal.org/node/2322097
Merge pull request #41 from Jbekker/add-data_table-definition

Issue #2323775 Define data_tables for our translatable entities