Add log4j-streams module.

  - See LOG4J2-547
  - Thanks to Bruce Brouwer for the patch!
  - Added finals everywhere to said patch.

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1587396 13f79535-47bb-0310-9956-ffa450edef68