Created by: wangkuiyi

Fixes https://github.com/PaddlePaddle/Paddle/issues/816

In this PR,

1. I initialize Bazel WORKSPACE file to declare an external dependency to https://github.com/pubref/rules_protobuf, which implements the Google-style protobuf building rules.

   For more information please refer to this example repo: https://github.com/wangkuiyi/learn-bazel.

2. I also add a simple package in /third_party/protobuf_test to demonstrate using protobuf and gtest.

3. I updated the docker_install_en.rst documents to show how we can develop using Docker and Bazel.

Dear reviewers:

Please feel free to use Docker and Bazel to check this PR as described in my update to Docker document in this PR.