Fixed phpdoc
Store null as empty value instead of zero
EZP-20936: restore sort key for field definition default value
EZP-20936: implement KeywordStorage::deleteFieldData()
EZP-20936: added tests for removing and adding field definition
EZP-20936: added test overrides for Rating and User field types
Merge pull request #403 from ezsystems/fix-EZP-20936-fieldtype-integration-tests

Fix EZP- 20936: update fieldtype integration tests for adding and removing field definition