@Override
    public T remove(final int index) {
        return removeInternal(groupForInternal(index), index);
    }
Creates new grouped list
@param list container to be used by this group list.
            WARNING: GroupList assumes to be the sole manipulator of this list. Parallel editing in other places leads to undefined behaviour
@param defaultGroup default group to assign to new/first element when list is empty
main/src/main/java/cgeo/geocaching/utils/GroupedList.java