vfs_fruit: add fruit:model = <modelname> parametric option

vfs_fruit: add fruit:model = <modelname> parametric option

fruit:model = iMac
fruit:model = MacBook
fruit:model = MacPro
fruit:model = Xserve

will all display a different icon inside Finder.

Formerly, we used "Samba" which resulted in a "?" icon in Finder, with
the new default "MacSamba" we appear with a computer box icon at least.

Guenther

Bug: https://bugzilla.samba.org/show_bug.cgi?id=12840

Signed-off-by: Guenther Deschner <gd@samba.org>
Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>
Autobuild-User(master): Günther Deschner <gd@samba.org>
Autobuild-Date(master): Wed Jul 12 03:17:57 CEST 2017 on sn-devel-144