docs: fix a link, add PanelBar to the widgets aware of DS hierarchy (#2620)

Author: Desislava Mihaylova

docs/api/javascript/ui/dropdownlist.md

@@ -1783,7 +1783,7 @@ The widget instance which fired the event.
 Fired when an item from the popup is selected by the user either with mouse/tap or with keyboard navigation.
 
 > * The event is not fired when an item is selected programmatically.
-> * Since version Q1 2015 (2015.1.318), the [option label has been moved outside the item list DOM collection](/backward-compatibility#kendo-ui-2015-q1). As a result, `jQuery.index()` can no longer be used to reliably detect if the option label is the selected dropdown item. A more appropriate approach would be to check if the selected dataItem value is an empty string, and/or check if the selected dateItem's text is equal to the `optionLabel` string.
+> * Since version Q1 2015 (2015.1.318), the [option label has been moved outside the item list DOM collection]({% slug breakingchanges2015_kendoui %}#kendo-ui-2015-q1). As a result, `jQuery.index()` can no longer be used to reliably detect if the option label is the selected dropdown item. A more appropriate approach would be to check if the selected dataItem value is an empty string, and/or check if the selected dateItem's text is equal to the `optionLabel` string.
 >   *  `e.sender.dataItem(e.item)[e.sender.options.dataValueField] == ""`
 >   *  `e.sender.dataItem(e.item)[e.sender.options.dataTextField] == e.sender.options.optionLabel`
 

docs/framework/hierarchicaldatasource/overview.md

@@ -205,7 +205,7 @@ The configuration above creates a two-level HierarchicalDataSource—categor
 
 ### Bind Widgets to HierarchicalDataSource
 
-At this time, the only widget that is aware of the dataSource hierarchy is the TreeView. However, since the HierarchicalDataSource component inherits from the DataSource component, you can share the root level of the hierarchy with any DataSource-enabled component.
+Currently, the Kendo UI widgets that are aware of the dataSource hierarchy are the TreeView and the PanelBar. However, since the HierarchicalDataSource component inherits from the DataSource component, you can share the root level of the hierarchy with any DataSource-enabled component.
 
 ### Share HierarchicalDataSource between Widgets