PIM-1647 [Mass Edit Action] Add products to groups

```
Bug fix: yes
Feature addition: yes
Backwards compatibility break: no
Unit test passes: yes
Behat scenarios passes: yes
Checkstyle issues: no
ChangeLog updated: yes
Documentation PR:
Fixes the following jira:
 - PIM-1647
 - potentially another one about edit common attributes mass edit action that allows editing
   all the attributes (even if not in common). This causes a fatal error, because it will try
   to set the data on a null value (as the product value cannot be retrieved from the product).
```