Upgrade to angular-ui-tree 2.5.0

With >=2.10.0 there is an error "context is null" if start dragging.
With >=2.6.0 there is a missing angular 1.4 dependency.

bower.json

@@ -18,7 +18,7 @@
     "angular-ui-router": "~0.2.15",
     "angular-ui-select": "~0.13.1",
     "angular-ui-switch": "~0.1.1",
-    "angular-ui-tree": "~2.2.0",
+    "angular-ui-tree": "~2.5.0",
     "angular-gettext": "~2.1.2",
     "angular-scroll-glue": "~2.0.6",
     "ngBootbox": "~0.1.2",

openslides/agenda/static/templates/agenda/item-sort.html

@@ -13,8 +13,8 @@
 <div class="details">
   <p class="lead" translate>Drag and drop items to change the order of the agenda. Your modification will be saved immediately.</p>
 
-  <div ui-tree callbacks="treeOptions">
-    <ol ui-tree-nodes="" ng-model="items" id="tree-root">
+  <div ui-tree="treeOptions" id="tree-root">
+    <ol ui-tree-nodes ng-model="items">
       <li ng-repeat="item in items" ui-tree-node ng-include="'nodes_renderer.html'">
     </ol>
   </div>