Move client/unversioned/remotecommand to client-go

Module remotecommand originally part of kubernetes/pkg/client/unversioned was moved
to client-go/tools, and will be used as authoritative in kubectl, e2e and other places.

Module remotecommand relies on util/exec module which will be copied to client-go/pkg/util

Kubernetes-commit: 2612e0c78ad18ac87bbd200d547100cf99f36089

tools/remotecommand/doc.go

@@ -0,0 +1,20 @@
+/*
+Copyright 2015 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 remotecommand adds support for executing commands in containers,
+// with support for separate stdin, stdout, and stderr streams, as well as
+// TTY.
+package remotecommand // import "k8s.io/client-go/tools/remotecommand"