Port to gsettings -- take 2

Created by: GeraldJansen

This PR is an attempt to move forward on #470, resolving a few recently created conflicts with the master branch. All the credit for the work done goes to @bgamari.

In addition to merging upstream/master, the only (minor) addition involves changing the gschema path and id to org.gnome.Hamster to be consistent with the dbus interface.