Add capability to filter out Heartbeats to to SLF4JLog and others

ScreenLog is currently the only logger to allow for filtering out of heartbeats.
Idea situation would be to have one unified way to filter out heartbeats for all the loggers.

In slf4j logger, it's trivial to implement by just adding another special logger category that can be filtered out in log4j.properties.

However, since the strings created are pretty large, it may actually be a lot more efficient to intercept it at a higher level and just not print altogether, hopefully saving some string concats along the way.