SLF4J , Simple Logging Facade for Java#

website JIRA issue 376

Steps#

1. run the slf4j migrator
2. add the slf4j-log4j12.jar to the eclipse buildpath
3. change build.xml so that slf4j-log4j12.jar is added to WEB-INF/lib
4. test with tomcat
5. test with WebSphere (old JSPWiki version and new (slf4j) JSPWiki version