Enables listview children in dialog trees

By default trees doesnt show children of listview nodes, this enables
them in dialog trees, otherwise content pickers cannot select childrens
of a listview node

src/Umbraco.Web/Trees/ContentTreeController.cs

@@ -98,7 +98,8 @@ namespace Umbraco.Web.Trees
             {
 
                 //Special check to see if it ia a container, if so then we'll hide children.
-                var isContainer = e.IsContainer();
+                //we only perform this check for non-dialog trees since pickers needs access to these nodes
+                var isContainer = e.IsContainer() && (queryStrings.Get("isDialog") != "true");
 
                 var node = CreateTreeNode(
                     e.Id.ToInvariantString(),

src/Umbraco.Web/Trees/ContentTreeControllerBase.cs

@@ -177,11 +177,13 @@ namespace Umbraco.Web.Trees
             //before we get the children we need to see if this is a container node
             var current = Services.EntityService.Get(int.Parse(id), UmbracoObjectType);
 
-            if (current != null && current.IsContainer())
+
+            if (queryStrings.Get("isDialog") != "true" && current != null && current.IsContainer())
             {
                 //no children!
                 return new TreeNodeCollection();
             }
+
             return PerformGetTreeNodes(id, queryStrings);
         }
 

src/Umbraco.Web/Trees/MediaTreeController.cs

@@ -78,7 +78,7 @@ namespace Umbraco.Web.Trees
             var entity = (UmbracoEntity)e;
 
             //Special check to see if it ia a container, if so then we'll hide children.
-            var isContainer = entity.IsContainer();
+            var isContainer = e.IsContainer() && (queryStrings.Get("isDialog") != "true");
 
             var node = CreateTreeNode(
                 e.Id.ToInvariantString(),
@@ -89,6 +89,8 @@ namespace Umbraco.Web.Trees
                 entity.HasChildren && (isContainer == false));
 
             node.AdditionalData.Add("contentType", entity.ContentTypeAlias);
+            
+
 
             if (isContainer)
                 node.SetContainerStyle();