Support bucket versioning (#9377)

- Implement a new xl.json 2.0.0 format to support,
  this moves the entire marshaling logic to POSIX
  layer, top layer always consumes a common FileInfo
  construct which simplifies the metadata reads.
- Implement list object versions
- Migrate to siphash from crchash for new deployments
  for object placements.

Fixes #2111

go.mod

@@ -23,6 +23,7 @@ require (
 	github.com/coreos/go-semver v0.3.0 // indirect
 	github.com/coreos/go-systemd v0.0.0-20190321100706-95778dfbb74e // indirect
 	github.com/coreos/pkg v0.0.0-20180928190104-399ea9e2e55f // indirect
+	github.com/dchest/siphash v1.2.1
 	github.com/dgrijalva/jwt-go v3.2.0+incompatible
 	github.com/djherbis/atime v1.0.0
 	github.com/dustin/go-humanize v1.0.0
@@ -102,7 +103,6 @@ require (
 	github.com/soheilhy/cmux v0.1.4 // indirect
 	github.com/spaolacci/murmur3 v1.1.0 // indirect
 	github.com/streadway/amqp v0.0.0-20190404075320-75d898a42a94
-	github.com/stretchr/testify v1.5.1 // indirect
 	github.com/tinylib/msgp v1.1.1
 	github.com/tmc/grpc-websocket-proxy v0.0.0-20190109142713-0ad062ec5ee5 // indirect
 	github.com/ugorji/go v1.1.5-pre // indirect