PIM-870 : Create the product datagrid for the variant edit view

Bug fix: [no]
Feature addition: [yes]
Backwards compatibility break: [no]
Unit test passes: [yes]
Behat scenarios passes: [yes]
Checkstyle issues: [no]*
Fixes the following jira:
 - PIM-838
 - PIM-870
 - PIM-871
 - PIM-872