Add ability to turn on TRACE logging to log invocation times

Here are the requirements:

1. Turn on with a system property; zero perf impact if off: jboss.ejb.client.log.invocation-times
2. Use System.nanoTime() to capture stamps before and after org.jboss.ejb.client.EJBInvocationHandler#invoke and calculate the time from the difference; filter out negative times (can happen on certain multi-CPU system types)
3. Log the time in milliseconds including fraction part
4. Use a specific log category so that the trace can also be controlled by category