1.27

• weed shell add a few real commands
  • list volumes
  • list collections
  • file system disk usage
  • fix under-replicated volumes
• weed filer:
  • fix gRpc port to port + 10000
  • notification: add Go CDK pubsub support (#895 by @jba from Google)
• weed benchmark
  • add replication flag (#893 by @PapaYofen from SenseTime)
• weed master
  • add option to disable http, only uses gRpc
• miscellaneous bugs: #886