'Get the setting named key. First looks for a device specific setting.
If that is not found looks for a device default and if that is not
found uses the global default.'

@classmethod
def get_pref(cls, key):

    if (not cls.opts):
        cls.opts = cls.settings()
    try:
        return getattr(cls.opts, key)
    except:
        debug_print('KoboTouch::get_prefs    -    probably    an    extra_customization:', key)
    return None
