Bootstrap listener for custom Log4J initialization in a web environment.
Delegates to Log4jWebConfigurer (see its javadoc for configuration details).
WARNING: Assumes an expanded WAR file, both for loading the configuration
file and for writing the log files. If you want to keep your WAR unexpanded or
don't need application-specific log files within the WAR directory, don't use
Log4J setup within the application (thus, don't use Log4jConfigListener or
Log4jConfigServlet). Instead, use a global, VM-wide Log4J setup (for example,
in JBoss) or JDK 1.4's java.util.logging (which is global too).
This listener should be registered before ContextLoaderListener in web.xml,
when using custom Log4J initialization.
For Servlet 2.2 containers and Servlet 2.3 ones that do not
initalize listeners before servlets, use Log4jConfigServlet.
See the ContextLoaderServlet javadoc for details.