Use g_timeout_add_seconds() for power efficiency

This attempts to align second-granularity wakeups across the system,
reducing CPU wakeups a little.

I considered all timeouts of duration 1 second or greater, and moved
the non-timing-critical ones to g_timeout_add_seconds(). (Actually,
I didn't find any that I felt were timing-critical)

src/sugar/gsm-session.c

@@ -203,7 +203,7 @@ start_phase (GsmSession *session)
     {
       if (session->phase < GSM_SESSION_PHASE_APPLICATION)
 	{
-	  session->timeout = g_timeout_add (GSM_SESSION_PHASE_TIMEOUT * 1000,
+	  session->timeout = g_timeout_add_seconds (GSM_SESSION_PHASE_TIMEOUT,
 					    phase_timeout, session);
 	}
     }