no-jira : slf4j troubles: using slf4j-api 1.6.1, and switching from slf4j-log4j12 to log4j-over-slf4j due to jetty slf4j dependencies for testing

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1573022 13f79535-47bb-0310-9956-ffa450edef68