Add knative serving v1alpha1 to generate CRD command

This commit adds the ability to generate a knative serving
definition from the Function Store or a stack.yaml file with
a basic definition including: namespace, name, env-vars and
image.

Tested with Istio on Packet.net using figlet.

Signed-off-by: Alex Ellis <alexellis2@gmail.com>

schema/knative/v1alpha1/serving.go

@@ -0,0 +1,48 @@
+// Copyright (c) OpenFaaS Author(s) 2019. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+package v1alpha1
+
+import "github.com/openfaas/faas-cli/schema"
+
+const APIVersionLatest = "serving.knative.dev/v1alpha1"
+
+//ServingSpec describe characteristics of the object
+type ServingSpec struct {
+	RunLatest ServingSpecRunLatest `yaml:"runLatest"`
+}
+
+type ServingSpecRunLatest struct {
+	Configuration ServingSpecRunLatestConfiguration `yaml:"configuration"`
+}
+type ServingSpecRunLatestConfiguration struct {
+	RevisionTemplate ServingSpecRunLatestConfigurationRevisionTemplate `yaml:"revisionTemplate"`
+}
+
+type ServingSpecRunLatestConfigurationRevisionTemplate struct {
+	Spec ServingSpecRunLatestConfigurationRevisionTemplateSpec `yaml:"spec"`
+}
+
+type ServingSpecRunLatestConfigurationRevisionTemplateSpec struct {
+	Container ServingSpecRunLatestConfigurationRevisionTemplateSpecContainer `yaml:"container"`
+}
+
+type ServingSpecRunLatestConfigurationRevisionTemplateSpecContainer struct {
+	Image string    `yaml:"image"`
+	Env   []EnvPair `yaml:"env,omitempty"`
+}
+
+type EnvPair struct {
+	Name  string `yaml:"name"`
+	Value string `yaml:"value"`
+}
+
+//ServingCRD root level YAML definition for the object
+type ServingCRD struct {
+	//APIVersion CRD API version
+	APIVersion string `yaml:"apiVersion"`
+	//Kind kind of the object
+	Kind     string          `yaml:"kind"`
+	Metadata schema.Metadata `yaml:"metadata"`
+	Spec     ServingSpec     `yaml:"spec"`
+}