Clarify split package in docs.

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1588800 13f79535-47bb-0310-9956-ffa450edef68
Clean up log4j-slf4j-impl OSGi build.

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1588801 13f79535-47bb-0310-9956-ffa450edef68