WriteExcel - xl_object to 'rwp' and _set_xl_object to set it

moved worksheet_name validation from 'around' to trigger; moved filetype-from-filename regex capture from BUILD block to filetype builder

WriteExcel: * set worksheet name * use scalar filehandle for xlsx filetype to allow both data return and file save functions * seperate _write_xlsx_row() function to handle write_row and write_bold_row * row counter starts at A1, auto-increments as expected (A2, A3, etc) * changes should allow call to both data() & save() for both filetypes

first draft of Local::WriteExcel - creates xls or xlsx file using Spreadsheet::WriteExcel::Simple syntax * can save file or return data for xls file but only save xlsx file