The fstab backend exposes server and sharename as product and vendor
properties, but had the meaning backwards (the product is subordinate to
the vendor, as is the sharename to the server).

Also allow translation of the description property.

[solid/fstab] Add support for x-gvfs style options in fstab

This fstab options allows an administrator to specify names and icons
intended for the user, shown in a GUI
For details, see https://git.gnome.org/browse/gvfs/tree/monitor/udisks2/what-is-shown.txt