Add Logger/LoggerProvider to support new Log4j 2 to improve performance

The new Log4j 2 project will be released soon. It has major improvements over Log4j and Logback. Currently, JBoss Logging can log to Log4j 2 indirectly by way of SLF4J (if the log4j-slf4j artifact is on the classpath) or the Log4j 1.2 API (if the log4j-1.2-api artifact is on the classpath and when JBLOGGING-94 is fixed). However, performance would be improved if JBoss Logging could log directly to the Log4j 2 API.

Looks like we just need a new Log4j2Logger and Log4j2LoggerProvider. I'll try to submit a pull request in the next few weeks. I'm currently working on other tasks in Log4j 2.