Don't log WARN

As prescribed at http://www.techempower.com/benchmarks/#section=code do as less logging as possible

wicket/src/main/resources/log4j.properties

@@ -2,11 +2,11 @@ log4j.appender.Stdout=org.apache.log4j.ConsoleAppender
 log4j.appender.Stdout.layout=org.apache.log4j.PatternLayout
 log4j.appender.Stdout.layout.conversionPattern=%-5p - %-26.26c{1} - %m\n
 
-log4j.rootLogger=WARN,Stdout
+log4j.rootLogger=ERROR,Stdout
 
-log4j.logger.org.apache.wicket=WARN
-log4j.logger.org.apache.wicket.protocol.http.HttpSessionStore=WARN
-log4j.logger.org.apache.wicket.version=WARN
-log4j.logger.org.apache.wicket.RequestCycle=WARN
+log4j.logger.org.apache.wicket=ERROR
+log4j.logger.org.apache.wicket.protocol.http.HttpSessionStore=ERROR
+log4j.logger.org.apache.wicket.version=ERROR
+log4j.logger.org.apache.wicket.RequestCycle=ERROR