plugin base: let plugins decide if they should be sorted last

Note that even if a plugin says it wants to be sorted last, the generic plugin
will always be the last one. Also, there is no order guaranteed between two
plugins that request to be sorted last.

src/mm-plugin-base.c

@@ -65,11 +65,13 @@ typedef struct {
     char *name;
     GUdevClient *client;
     GHashTable *tasks;
+    gboolean sort_last;
 } MMPluginBasePrivate;
 
 enum {
     PROP_0,
     PROP_NAME,
+    PROP_SORT_LAST,
     LAST_PROP
 };
 
@@ -1216,6 +1218,12 @@ get_name (MMPlugin *plugin)
     return MM_PLUGIN_BASE_GET_PRIVATE (plugin)->name;
 }
 
+static gboolean
+get_sort_last (const MMPlugin *plugin)
+{
+    return MM_PLUGIN_BASE_GET_PRIVATE (plugin)->sort_last;
+}
+
 static char *
 get_driver_name (GUdevDevice *device)
 {
@@ -1387,6 +1395,7 @@ plugin_init (MMPlugin *plugin_class)
 {
     /* interface implementation */
     plugin_class->get_name = get_name;
+    plugin_class->get_sort_last = get_sort_last;
     plugin_class->supports_port = supports_port;
     plugin_class->cancel_supports_port = cancel_supports_port;
     plugin_class->grab_port = grab_port;
@@ -1424,6 +1433,10 @@ set_property (GObject *object, guint prop_id,
         /* Construct only */
         priv->name = g_value_dup_string (value);
         break;
+    case PROP_SORT_LAST:
+        /* Construct only */
+        priv->sort_last = g_value_get_boolean (value);
+        break;
     default:
         G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
         break;
@@ -1440,6 +1453,9 @@ get_property (GObject *object, guint prop_id,
     case PROP_NAME:
         g_value_set_string (value, priv->name);
         break;
+    case PROP_SORT_LAST:
+        g_value_set_boolean (value, priv->sort_last);
+        break;
     default:
         G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
         break;
@@ -1482,6 +1498,15 @@ mm_plugin_base_class_init (MMPluginBaseClass *klass)
                               NULL,
                               G_PARAM_READWRITE | G_PARAM_CONSTRUCT_ONLY));
 
+    g_object_class_install_property
+        (object_class, PROP_SORT_LAST,
+         g_param_spec_boolean (MM_PLUGIN_BASE_SORT_LAST,
+                               "Sort Last",
+                               "Whether the plugin should be sorted last in the"
+                               "list of plugins loaded",
+                               FALSE,
+                               G_PARAM_READWRITE | G_PARAM_CONSTRUCT_ONLY));
+
     signals[PROBE_RESULT] =
         g_signal_new ("probe-result",
                       G_OBJECT_CLASS_TYPE (object_class),