This comment probably breaks the crap out of 'agent' but 'agent2' is the
future.

agent2 should now successfully use the new config parser w/ codec
support.

No 'conditionals' support yet, but I will add that soon.

Rough list of changes:
- try to unify agent2 errors
- make codecs loaded the same way other plugins are (removes extlib,
  woot)
- make default values subject to validation (necessary for codecs)
- some style cleanup
- move more error messages into locales/en.yml
- fix LogStash::Event#to_s to use %{+...}