Fix some bugs and improve tests of configurations:
- fix bug relative to empty templates
- disable events during validation to open silently the active workbooks
- fix bug relative to deep path exportations
Fix Issue #28 :
- add a function vtkDefaultExcelExtension in vtkExcelUtilities module
- add a test for the new function
- divide vtkExcelUtilities in two version for 2003 and 2007
430 Tests OK in 177 seconds. No failure.