Fixed LOG4J2-452 (Part 1-Code) Added a ServletContext attribute that, when set to 'true', disables Log4j's auto-initialization in Servlet 3.0+ web applications. Will update documentation in Part 2 commit.

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1561958 13f79535-47bb-0310-9956-ffa450edef68