This function tries to open a Microsoft Excel
(xls/xlsx) file or an openxlsx Workbook with the proper
application, in a portable manner.
In Windows (c) and Mac (c), it uses system default handlers,
given the file type.
In Linux it searches (via which
) for available xls/xlsx
reader applications (unless options('openxlsx.excelApp')
is set to the app bin path), and if it finds anything, sets
options('openxlsx.excelApp')
to the program choosen by
the user via a menu (if many are present, otherwise it will
set the only available). Currently searched for apps are
Libreoffice/Openoffice (soffice
bin), Gnumeric
(gnumeric
) and Calligra Sheets (calligrasheets
).