Fix Eclipse compile errors

* Most web.xml servlet API versions updated to 3.0 for ASYNC support
* httpsession-xml is left at 2.5 to ensure compatability & remove ASYNC
* Remove @Override on interface override

samples/httpsession-xml/src/main/webapp/WEB-INF/web.xml

@@ -25,7 +25,6 @@
 		<url-pattern>/*</url-pattern>
                 <dispatcher>REQUEST</dispatcher>
                 <dispatcher>ERROR</dispatcher>
-                <dispatcher>ASYNC</dispatcher>
 	</filter-mapping>
 	<!-- end::springSessionRepositoryFilter[] -->