[LOG4J2-583] TCP and UDP socket servers should be able to handle XML log events. Refactor current code for XML and JSON. Create stubs for XML and JSON implementations.

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1582205 13f79535-47bb-0310-9956-ffa450edef68