Remove st_container_remove_all & rewrite st_container_destroy_children

1. Both functions leaked the nodes in priv->children
2. st_container_remove_all wasn't properly updating first_child and last_child
3. remove_all() is almost never right since it won't cause signal handlers
   on the children to be removed. In the rare cases where it might be needed
   the caller can simply use clutter_container_remove().
https://bugzilla.gnome.org/show_bug.cgi?id=640781

js/ui/dash.js

@@ -206,7 +206,7 @@ Dash.prototype = {
 
     _redisplay: function () {
         this._box.hide();
-        this._box.remove_all();
+        this._box.destroy_children();
 
         let favorites = AppFavorites.getAppFavorites().getFavoriteMap();
 

js/ui/endSessionDialog.js

@@ -470,7 +470,7 @@ EndSessionDialog.prototype = {
     OpenAsync: function(type, timestamp, totalSecondsToStayOpen, inhibitorObjectPaths, callback) {
         this._totalSecondsToStayOpen = totalSecondsToStayOpen;
         this._inhibitors = [];
-        this._applicationList.remove_all();
+        this._applicationList.destroy_children();
         this._type = type;
 
         if (!(this._type in DialogContent))

js/ui/modalDialog.js

@@ -83,7 +83,7 @@ ModalDialog.prototype = {
     },
 
     setButtons: function(buttons) {
-        this._buttonLayout.remove_all();
+        this._buttonLayout.destroy_children();
         let i = 0;
         for (let index in buttons) {
             let buttonInfo = buttons[index];

js/ui/workspacesView.js

@@ -769,7 +769,7 @@ WorkspaceIndicatorPanel.prototype = {
         else
             this.actor.set_skip_paint(this._box, false);
 
-        this._box.remove_all();
+        this._box.destroy_children();
         for (let i = 0; i < this._workspaces.length; i++) {
             let actor = new St.Button({ style_class: 'workspace-indicator',
                                         track_hover: true });