export description

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imported from sf tracker
id 1013087
http://sourceforge.net/support/tracker.php?aid=1013087
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Feature Request:
Add some desc or info to export header and footer:
currently the table caption and footer can not be
exported. I read another request comments said that
footer contains html stuff and won't suppose to export.
However, it would be nice if there are option to export
some desc in the beginning and at the end.
like user can define:

export.header= some desc about table content,
export.footer= some desc or summay for the table

and the real export will looks like:
........export.header......
..current table export......
......export.footer......