Start up in daemon mode when GNOME starts

Hat tip to Guido for the session.{c,h} files.

Closes #45

src/calls-application.c

@@ -34,6 +34,7 @@
 #include "calls-call-window.h"
 #include "calls-main-window.h"
 #include "calls-application.h"
+#include "session.h"
 
 #define HANDY_USE_UNSTABLE_API
 #include <handy.h>
@@ -402,6 +403,8 @@ constructed (GObject *object)
                                    actions, G_N_ELEMENTS (actions), self);
   g_object_unref (action_group);
 
+  calls_session_register (APP_ID);
+
   parent_class->constructed (object);
 }
 
@@ -411,6 +414,8 @@ dispose (GObject *object)
 {
   CallsApplication *self = (CallsApplication *)object;
 
+  calls_session_unregister ();
+
   g_clear_object (&self->call_window);
   g_clear_object (&self->main_window);
   g_clear_object (&self->record_store);