Update cs_power.py

Allow for longer times till the system goes to sleep - added 2 and 3 hours. 
This is useful when listening to albums ( > 60 min) without having to move the mouse or watching movies. 
Maybe this could/should be fixed else where for all different media/video players and maybe browsers (html5 or flash) but given the simplicity of this solution I guess this is useful already - See feature request  linuxmint#6185

I tested the "fix" (actually just additional options) but the translation(s) for "hours" are missing afterwards. 
Where or how can I add translations?

files/usr/share/cinnamon/cinnamon-settings/modules/cs_power.py

@@ -40,6 +40,8 @@
     (1800, _("30 minutes")),
     (2700, _("45 minutes")),
     (3600, _("1 hour")),
+    (7200, _("2 hours")),
+    (10800, _("3 hours")),
     (0, _("Never"))
 ]