Fix wrong package name in webapp manual.

  - Fixes LOG4J2-740.

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1613336 13f79535-47bb-0310-9956-ffa450edef68
Add changelog entry for LOG4J2-740.

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1613337 13f79535-47bb-0310-9956-ffa450edef68