Diagram switch to UML, better section title »Interfaces and sorting«

Doc/Sd1/interfacesAbstractClasses.xml

@@ -449,8 +449,8 @@ public interface MyFlushable extends MyAutoCloseable {
     </itemizedlist>
   </figure>
 
-  <section xml:id="sw1SectSortingRectangles">
-    <title>Sorting <classname>Rectangle</classname> instances</title>
+  <section xml:id="sw1SectInterfacesSorting">
+    <title>Interfaces and sorting</title>
 
     <figure xml:id="sd1_fig_StringInterfaces">
       <title>Interfaces implemented by class <classname