Upgrade the way framework core is shut down to also allow for webapp context shutdowns

Shutdown of a web application under Tomcat sometimes leaves exceptions due to non-up-to-date ability to deal with web application shutdown events. Specifically, we need the following:

(1) An implementation of javax.servlet.ServletContextListener in every web application
(2) Appropriate locking to prevent an already-shut-down web application from trying to shut itself down another time
(3) The following addition to the web.xml file for the web applications:

<web-app>
    <!-- Usual stuff here -->
    <listener>
        <listener-class&gt;com.mycompany.MyClass</listener-class&gt;
    </listener>
</web-app>