Log filter

- exclusion filter.
- config to control the exclusion filter.
- prefix all loggers with st2 so that the name filter always works.
No. In the format for a log line we typically use %(module)s instead of %(name)s therefore it will not show up. See https://github.com/StackStorm/st2/blob/master/st2reactor/conf/logging.sensorcontainer.conf#L33.