skip gsettings that don't exist
idle-activation-enabled (in org.gnome.desktop.screensaver) is deprecated,
we need to clamp idle-delay (in org.gnome.desktop.session) to 0
fixed deprecated GObject attributes
fixed signal handling (see https://bugzilla.gnome.org/show_bug.cgi?id=689208)
listen to ConsoleKit signals

this is untested since i'm not using consolekit
ConsoleKit manager might not even exist
let's clearly label the object path
match by interface only
also listen for signals from logind;
introduced more complexity into main() than is probably necessary
updated changelog, readme;
bumped version number
Merge branch 'ubuntu-13.10-fixes'