code: private <T> boolean addToListInternal(Collection<T> list, T value) {
          if (!list.contains(value)) {
              list.add(value);
              isModified = true;
              return true;
          } else {
              return false;
          }
      }
docs: Add a value to given list, making the Project modified if the value is
  not already present in the list.
  
  @param list
  the list
  @param value
  the value to be added
  @return true if the value was not already present in the list, false
  otherwise