Get cmd uses print-column extn from Openapi schema

Get command now uses metadata x-kubernetes-print-columns, if present, in Openapi schema
to format output for a resource. This functionality is guarded by a boolean
flag 'use-openapi-print-columns'.

pkg/kubectl/cmd/util/openapi/BUILD

@@ -12,6 +12,7 @@ go_library(
     name = "go_default_library",
     srcs = [
         "doc.go",
+        "extensions.go",
         "openapi.go",
         "openapi_cache.go",
         "openapi_getter.go",

pkg/kubectl/cmd/util/openapi/extensions.go

@@ -0,0 +1,26 @@
+/*
+Copyright 2017 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package openapi
+
+import "github.com/go-openapi/spec"
+
+const PrintColumnsKey = "x-kubernetes-print-columns"
+
+// GetPrintColumns looks for the open API extension for the display columns.
+func GetPrintColumns(extensions spec.Extensions) (string, bool) {
+	return extensions.GetString(PrintColumnsKey)
+}

pkg/kubectl/cmd/util/openapi/openapi.go

@@ -194,7 +194,7 @@ func (o *Resources) parseDefinition(name string, s spec.Schema) Kind {
 		Fields:           map[string]Type{},
 	}
 	if err != nil {
-		glog.Warning(err)
+		glog.V(2).Info(err)
 	}
 
 	// Definition represents a primitive type - e.g.