Specify default Facility level in FlumeAppender.

  - Due to my recent changes involving how plugins are constructed, 
  this value had to be manually specified. Without the value, it 
  would cause an NPE later on.

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1597481 13f79535-47bb-0310-9956-ffa450edef68
Add interface for building plugins in Java instead of XML/JSON.

  - Part of LOG4J2-653.

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1597484 13f79535-47bb-0310-9956-ffa450edef68
ported SimplePerfTest to JMH

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1597485 13f79535-47bb-0310-9956-ffa450edef68
Add @Documented, some docs, and ElementType.FIELD.

  - Also added defaultValue attribute to @PluginAttribute to replace 
  the @PluginDefault annotation.

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1597486 13f79535-47bb-0310-9956-ffa450edef68
Add clearer documentation on @PluginValue.

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1597487 13f79535-47bb-0310-9956-ffa450edef68
removed wrong comment (copy&paste mistake)

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1597488 13f79535-47bb-0310-9956-ffa450edef68