code: public static <T> DataKey<T> create(String name, Class<T> dataClass) {
          return create(name, dataClass, true, null);
      }
docs: creates a data key with the given name and type. This data
  key allows for null values and sets no default value.
  
  @param <T> the type
  @param name the name of the key that is stored in the xdata file
  @param dataClass the type's class
  @return