improved syntax for retention specifications as in Bug #697896
improved syntax for retention specifications as in Bug #697896

deniszh/whisper,cbowman0/whisper,akbooer/whisper,piotr1212/whisper,penpen/whisper,obfuscurity/whisper,graphite-server/whisper,acdha/whisper,kerlandsson/whisper,graphite-project/whisper,alexandreboisvert/whisper,jjneely/whisper