recent: Port from GtkRecentManager to GBookmarkFile

GVfs dependency on GTK+ causes various issues. It is only needed by the
recent backend, which is based on GtkRecentManager. GtkRecentManager is
just wrapper for GBookmarkFile. Let's port the backend to use GBookmarkFile
and remove the unwanted GTK+ dependency.

https://bugzilla.gnome.org/show_bug.cgi?id=773300