Add OpenShift implementations of ImageSource and ImageDestination

Note that this assumes that both (docker login) and (oc login) has
happened, the credentials can be read from the usual config files,
and that the default OpenShift instance should be used.

This includes copy&pasted/modified/simplified code from OpenShift
and Kubernetes, primarily for config file parsing and setting up
TLS and HTTP authentication.

This is much smaller than linking to the upstream OpenShift client
libraries, which via various abstractions and registration drag in much
(dozens of megabytes) more code.

The primary loss from this simplification is automatic conversions
between various versions of the API objects, both for the REST API and
for local configuration storage.

This does not contain downloading/uploading signatures, which depends on
server-side support.

vendor/github.com/imdario/mergo/doc.go

@@ -0,0 +1,44 @@
+// Copyright 2013 Dario Castañé. All rights reserved.
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+/*
+Package mergo merges same-type structs and maps by setting default values in zero-value fields.
+
+Mergo won't merge unexported (private) fields but will do recursively any exported one. It also won't merge structs inside maps (because they are not addressable using Go reflection).
+
+Usage
+
+From my own work-in-progress project:
+
+	type networkConfig struct {
+		Protocol string
+		Address string
+		ServerType string `json: "server_type"`
+		Port uint16
+	}
+
+	type FssnConfig struct {
+		Network networkConfig
+	}
+
+	var fssnDefault = FssnConfig {
+		networkConfig {
+			"tcp",
+			"127.0.0.1",
+			"http",
+			31560,
+		},
+	}
+
+	// Inside a function [...]
+
+	if err := mergo.Merge(&config, fssnDefault); err != nil {
+		log.Fatal(err)
+	}
+
+	// More code [...]
+
+*/
+package mergo