add setting for nautilus-specific mount options

[Karl-Philipp Richter]

nautilus allows to mount devices to be mounted without bothering with the command line and `/etc/fstab`. Newer filesystems (btrfs, zfs (the latter currently not yet supported)) provide a lot of mount points controlling transparent compression, deduplication, etc. which would be great to have available for control in `nautilus`.

experienced with 3.10.1

ProblemType: Bug
DistroRelease: Ubuntu 14.10
Package: nautilus 1:3.10.1-0ubuntu15
Uname: Linux 3.17.4-031704-generic x86_64
NonfreeKernelModules: zfs zunicode zcommon znvpair zavl
ApportVersion: 2.14.7-0ubuntu8
Architecture: amd64
CurrentDesktop: Unity
Date: Sat Dec 6 05:15:38 2014
GsettingsChanges: b'org.gnome.nautilus.list-view' b'default-column-order' b"['name', 'size', 'type', 'date_modified', 'date_accessed', 'owner', 'group', 'permissions', 'mime_type', 'where']"
SourcePackage: nautilus
UpgradeStatus: No upgrade log present (probably fresh install)

[Sebastien Bacher (seb128)]

Thank you for your bug report. That's not something Ubuntu is going to add but it could be reported upstream on https://gitlab.gnome.org/GNOME/nautilus/issues which is a better place to discuss the feature