allow AbstractRemoveHardcodedI18nPropertiesTask-subclasses to add more properties to be removed.
The abstract class has a set of properties ("label", "confirmationMessage", "errorMessage", "i18nBasename", "description") which we want to get rid of and which are expected in mainly every app or module. Some modules - e.g. mediaeditor - have properties which are specific for them and which also should be removed (e.g. "trackingLabel" in mediaeditor ).