Checkin servlet-api-2.5 jar and update demo ant scripts to compile java classes at 1.8 (#2491)

* Demo portal is hosted in Google appengine. As the new appengine-java-sdk do not include (appengine Java 11 runtime) any web-serving framework, we need to check-in the servlet-api-2.5 jar seperately in java/demo/war/WEB-INF/lib, similar to commons packages.

* Making ant to compile demo class files at 1.8

java/demo/build.xml

@@ -30,7 +30,7 @@
       </fileset>
     </copy>
     <javac srcdir="src" destdir="war/WEB-INF/classes" classpathref="project.classpath" debug="on"
-           includeAntRuntime="false"/>
+           includeAntRuntime="false" source="1.8" target="1.8"/>
   </target>
 
   <target name="runserver" depends="compile" description="Starts the development server.">