Added notes to Tree and TreeTable about them using the old style data API.

Change-Id: I845a75b086bdf11f9c4545416c6126c404041ee8

documentation/components/components-tree.asciidoc

@@ -12,6 +12,11 @@ ifdef::web[]
 image:{live-demo-image}[alt="Live Demo", link="http://demo.vaadin.com/sampler/#ui/grids-and-trees/tree"]
 endif::web[]
 
+[NOTE]
+====
+[classname]#Tree# still uses the old data API from Vaadin 7.
+====
+
 The [classname]#Tree# component allows a natural way to represent data that has hierarchical relationships.
 The user can drill down in the hierarchy by expanding items by clicking on the expand arrow, and likewise collapse items.
 [classname]#Tree# is a selection component that allows selecting items.

documentation/components/components-treetable.asciidoc

@@ -12,6 +12,11 @@ ifdef::web[]
 image:{live-demo-image}[alt="Live Demo", link="http://demo.vaadin.com/sampler/#ui/grids-and-trees/tree-table"]
 endif::web[]
 
+[NOTE]
+====
+[classname]#TreeTable# still uses the old data API from Vaadin 7.
+====
+
 [classname]#TreeTable# is an extension of the [classname]#Table# component with
 support for a tree-like hierarchy in the first column. As with
 [classname]#Tree#, the hierarchy is determined by the parent-children