[gpm] Change critically low battery value

[Riccardo Romoli <ric romoli gmail com>]

Hi, in Debian Jessie running Gnome 3.14.1 I would change the "critically 
low battery value". So from dconf-editor I followed this path:

org.gnome.settings-daemon.plugins.power

The problem is that I haven't none of the following fields:
    time-action
    time-critical
    time-low
or
    use-time-for-policy
    percentage-action
    percentage-critical
    percentage-low

All the best, Riccardo