jcReadXls.java : fix bug where empty sheets would not have isReadDone set correctly

Signed-off-by: Mark Histed <mhisted@gmail.com>
frm_xlsfinfo: return sheets and sheetName in info

Signed-off-by: Mark Histed <mhisted@gmail.com>
xls2frm: error checking

Signed-off-by: Mark Histed <mhisted@gmail.com>
add cat_cellornum: will concatenate variables of cell or numeric types.  If all numeric, returns numeric.  If mixed numeric and cell, will convert numeric inputs to cell, cat, and return a cell.

Signed-off-by: Mark Histed <mhisted@gmail.com>