Output formatters and raw format

I don't want to use the logstash format, but I don't want to write my own output module either - the whole queuing and flushing stuff is good! So this lets you choose to either do the logstash munging, or just send the data through (mostly) as-is.

I think this isn't the right way to do it. Better would probably be to have a bunch of M::P::O::ES::Formatter::* modules and let the caller choose one, so we can have more on CPAN. But I don't actually need that and to do it right would mean learning more Moose than I have time for right now. So feel free to drop this on the floor.