Add a simple prototype "terminal" example.

examples/echo_terminal/terminal_client.mojom

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// TODO(vtl): Move this file somewhere sensible.
+
+module mojo.terminal;
+
+import "services/files/file.mojom";
+
+// Interface for applications that want to be able to be connected to by a
+// terminal. (Once connected, such an application will be able to write to/read
+// from the terminal by performing the corresponding operations on the provided
+// "file".)
+interface TerminalClient {
+  ConnectToTerminal(mojo.files.File terminal);
+};