public void insertColumn(int beforeIndex, Column<T, ?> col, Header<?> header) {
        insertColumn(beforeIndex, col, header, null);
    }
Inserts a column into the table at the specified index with an associated
header.

@param beforeIndex the index to insert the column
@param col         the column to be added
@param header      the associated {@link Header}
stroom-core-client-widget/src/main/java/com/google/gwt/user/cellview/client/AbstractCellTable.java