Need "DataSetHelpter" for worksheet also

```
When using ExcelLibrary.DataSetHelper.CreateWorkbook("Test.xls", ds) I am
unable to add worksheets to "Test.xls" it seems. Trying to use Workbook.Load
throws an error saying the stream is not writeable. What I'd like to do is:

Dim ws(3) As ExcelLibrary.SpreadSheet.Worksheet
ws(0) = New ExcelLibrary.SpreadSheet.Worksheet("Title")
ws(0).DataSetHelper(dataSet1)
ws(1) = New ExcelLibrary.SpreadSheet.Worksheet("Parts")
ws(1).DataSetHelper(dataSet2)
ws(2) = New ExcelLibrary.SpreadSheet.Worksheet("Analysis")
ws(2).DataSetHelper(dataSet3)
Dim wb As ExcelLibrary.SpeadSheet.Workbook = New
ExcelLibrary.SpreadSheet.Workbook()
wb.Worksheets.AddRange(ws)
wb.Save("Test.xls")
```

Original issue reported on code.google.com by `xstream....@gmail.com` on 20 Sep 2010 at 3:33

Start by tracing ExcelLibrary.DataSetHelper.CreateWorkbook, Workbook.Load, Worksheet, and Workbook.Save to understand how datasets and worksheet collections are handled. Reproduce the writeability error with the example, then verify that multiple worksheets can be populated from separate datasets and saved to Test.xls.

Written by the indexing model from the issue text.