bugfix: name of a field was added to the translation-catalogue when you used a translated label

added a return value to the trans and transChoice methods.

if you add a label in the configureFormFields-Method of your admin-class, the name of the field processed by the labelStrategy will still be added to the translation-catalogue. trans and transChoice have no return value, so in FormMapper isset($options['label']) will be false and labelStrategy will be used to get the label.