PIM-2492: Implements simple option filter on empty value
Update the changelog
PIM-2492: Make option filter empty work
PIM-2492: Clean OptionFilter class
PIM-2492: Filter by multi/simple values
PIM-2492: Filter by empty value for simpleselect
PIM-2492: Clean phpdoc
Add an option to add custom subscribers to the AttributeGroup form
Add a forgotten use statement
PIM-2492: Allow to filter by empty multi value
Allow filtering by decimal values in metric filter
Update change log
Product spec
Add product family spec
Use abstract classes and interfaces for CatalogBundle entities in specs (where possible)
Let's stick to 120 characters per line in specs too
Fix incorrect spec class name
Liberate specs from 'should'
Complete product categories spec
PIM-2492: Update scenarios