Attached is a patch that enhances the current Excel WFS output plugin. Better formatting and data truncation handling are added for Excel 97 files. Support for OOXML Excel 2007 files is also added (output format "excel2007").
Excel 2007 workbooks can handle up to 1,048,576 rows and 16,384 columns, so they are ideal for downloading large datasets. Unfortunately these large POI XML workbook objects also take up a huge amount of memory, so a workaround published by one of the POI authors is implemented for Excel 2007. If POI's memory usage improves in the future, the overriding Excel 2007 write method can be removed and the Excel 2007 output will use the standard POI ss usermodel.
Patch included updated test cases and also upgrades POI to version 3.7.