reference.conf: add empty listeners[]
EndOfPipeline: show object class
statistics JSON: cache->defragmenter
Use separate event loop groups

By default there's 2 * processors event loops and they're assigned in a
round-robin fashion within a group, so the current behaviour was very
much OK.

Still, this goes in the direction of clear-cut isolation between
listeners, which we feel strongly about.

Closes #54.
Merge pull request #60 from airbnb/pierre/listeners_in_reference_conf

reference.conf: add empty listeners[]
Merge pull request #62 from airbnb/pierre/stats_cache2defrag

statistics JSON: cache->defragmenter
Merge pull request #61 from airbnb/pierre/class_name_in_eop

EndOfPipeline: show object class
Merge pull request #63 from airbnb/pierre/autonomous_udp

Use separate event loop groups
UDPListenerTest: port comes from config

Not sure how that one got through automated tests.
plog-server: make Fragment a DefaultByteBufHolder
plog-server: move retention from ProtocolDecoder to Fragment

Seems a lot more readable to me.