EZP-21035: add BadStateException to ContentTypeService::addFieldDefinition()
EZP-21035: add BadStateException to ContentTypeHandler::addFieldDefinition()
EZP-21035: implement FieldType::isRepeatable()
EZP-21035: fixed checking Content instances for ezuser field
EZP-21035: implement ContentHandler::countInstancesOfContentType() and move logic to the BL
EZP-21035: renamed countInstancesOfContentType() to getContentCount()
EZP-21035: rename isRepeatable() to isSingular()
Merge pull request #422 from ezsystems/fix-EZP-21035-add-ezuser-field

Fix EZP-21035: User can not be properly created from inside storage