def addColumn(pageIndex=0, columnIndex=-1, retJson=True):
    """ Add a new column.

        @param pageIndex
        index of the page( default is 0, first page )

        @param columnIndex
        index of the column( default is -1, append to the end )

        @retJson
        format return value to json format or not( default True )

        @return
        a dict contains state of process, format like:
        {
            'success': True,
            'msg': 'Add column success.'
            'columnIndex': new column index(from 0)
        }

        """
