Add Support for Manta Object Storage as a Gateway (#5025)

Manta is an Object Storage by [Joyent](https://www.joyent.com/)

This PR adds initial support for Manta. It is intended as non-production 
ready so that feedback can be obtained.

vendor/github.com/joyent/triton-go/Gopkg.lock

@@ -0,0 +1,39 @@
+# This file is autogenerated, do not edit; changes may be undone by the next 'dep ensure'.
+
+
+[[projects]]
+  branch = "master"
+  name = "github.com/abdullin/seq"
+  packages = ["."]
+  revision = "d5467c17e7afe8d8f08f556c6c811a50c3feb28d"
+
+[[projects]]
+  name = "github.com/davecgh/go-spew"
+  packages = ["spew"]
+  revision = "346938d642f2ec3594ed81d874461961cd0faa76"
+  version = "v1.1.0"
+
+[[projects]]
+  branch = "master"
+  name = "github.com/hashicorp/errwrap"
+  packages = ["."]
+  revision = "7554cd9344cec97297fa6649b055a8c98c2a1e55"
+
+[[projects]]
+  branch = "master"
+  name = "github.com/sean-/seed"
+  packages = ["."]
+  revision = "e2103e2c35297fb7e17febb81e49b312087a2372"
+
+[[projects]]
+  branch = "master"
+  name = "golang.org/x/crypto"
+  packages = ["curve25519","ed25519","ed25519/internal/edwards25519","ssh","ssh/agent"]
+  revision = "bd6f299fb381e4c3393d1c4b1f0b94f5e77650c8"
+
+[solve-meta]
+  analyzer-name = "dep"
+  analyzer-version = 1
+  inputs-digest = "28853a8970ee33112a9e7998b18e658bed04d177537ec69db678189f0b8a9a7d"
+  solver-name = "gps-cdcl"
+  solver-version = 1