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/storage/client.go

@@ -0,0 +1,51 @@
+package storage
+
+import (
+	triton "github.com/joyent/triton-go"
+	"github.com/joyent/triton-go/client"
+)
+
+type StorageClient struct {
+	Client *client.Client
+}
+
+func newStorageClient(client *client.Client) *StorageClient {
+	return &StorageClient{
+		Client: client,
+	}
+}
+
+// NewClient returns a new client for working with Storage endpoints and
+// resources within CloudAPI
+func NewClient(config *triton.ClientConfig) (*StorageClient, error) {
+	// TODO: Utilize config interface within the function itself
+	client, err := client.New(config.TritonURL, config.MantaURL, config.AccountName, config.Signers...)
+	if err != nil {
+		return nil, err
+	}
+	return newStorageClient(client), nil
+}
+
+// Dir returns a DirectoryClient used for accessing functions pertaining to
+// Directories functionality of the Manta API.
+func (c *StorageClient) Dir() *DirectoryClient {
+	return &DirectoryClient{c.Client}
+}
+
+// Jobs returns a JobClient used for accessing functions pertaining to Jobs
+// functionality of the Triton Object Storage API.
+func (c *StorageClient) Jobs() *JobClient {
+	return &JobClient{c.Client}
+}
+
+// Objects returns an ObjectsClient used for accessing functions pertaining to
+// Objects functionality of the Triton Object Storage API.
+func (c *StorageClient) Objects() *ObjectsClient {
+	return &ObjectsClient{c.Client}
+}
+
+// SnapLinks returns an SnapLinksClient used for accessing functions pertaining to
+// SnapLinks functionality of the Triton Object Storage API.
+func (c *StorageClient) SnapLinks() *SnapLinksClient {
+	return &SnapLinksClient{c.Client}
+}