Beef up the warning message in case of excees worksheets.
Beef up the warning message in case of excees worksheets.

Warn the user that re-saving the document will permanently delete
those sheets that have not been loaded.  The current message doesn't
scare the user enough to take notice (apparently).

JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core