Let the IMPORT command handle siblings.

Let the IMPORT command handle siblings.

This works now:

     C> IMPORT --root=some<TAB>path
     S> INQUIRE DATA
     C> <element _name="a"/>
     C> <element _name="b"/>
     C> END

This changes the format of the IMPORT command. Rather using the
inquired data to retrieve the root element, the root element is now
specified with the command:

    IMPORT --root=path

When no --root option is specified the inquired elements are created
at the document root.