Add option to export and import snapshots

[kodebarista]

Currently we can create and restore different desktop layout using snapshots but if I want to use the same layout in another system I have to re-create the layout from scratch. It would be useful to have an option to import snapshots to quickly apply a theme that's already been formulated.

[edfloreshz]

With #87 it should now be possible to do this by finding the snapshot file and importing it, but I agree it would be useful to add an export/import button, thanks!