Generate javadocs as part of Maven site project reports

see http://maven.apache.org/plugins/maven-javadoc-plugin/usage.html

Change-Id: I6dc5dddea0adbb4abf5560d5d1c833408e944082
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
(cherry picked from commit a3d0b0d903)

pom.xml

@@ -463,6 +463,17 @@
     </plugins>
   </build>
 
+  <reporting>
+    <plugins>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-javadoc-plugin</artifactId>
+        <configuration>
+        </configuration>
+      </plugin>
+    </plugins>
+  </reporting>
+
   <dependencyManagement>
     <dependencies>
       <dependency>