PIM-1346 : Add filter and sorter on has product datagrid
PIM-1346 : Add forgotten documentation
PIM-1346 : Add a default sorting on identifier field
PIM-1346 : Add behat scenarios for sorting on has product column
PIM-1346 : Add behat scenario to filter by has product column in product variant group datagrid
Merge pull request #371 from akeneo/PIM-1346

PIM-1346 : Set has_product column sortable and filterable