update git clone instructions, a few other branches (#3895)

README.md

 <img src="docs/images/image-banner.png" align="middle" width="3000"/>
 
 # Unity ML-Agents Toolkit (Beta)
+[![docs badge](https://img.shields.io/badge/docs-reference-blue.svg)](https://github.com/Unity-Technologies/ml-agents/tree/release_1_docs/docs/)
-[![docs badge](https://img.shields.io/badge/docs-reference-blue.svg)](https://github.com/Unity-Technologies/ml-agents/tree/latest_release/docs/)
 [![license badge](https://img.shields.io/badge/license-Apache--2.0-green.svg)](LICENSE)
 
 ([latest release](https://github.com/Unity-Technologies/ml-agents/releases/tag/latest_release))

docs/Installation-Anaconda-Windows.md

 the ml-agents Conda environment by typing `activate ml-agents`)_:
 
 ```sh
-git clone --branch latest_release https://github.com/Unity-Technologies/ml-agents.git
+git clone --branch release_1 https://github.com/Unity-Technologies/ml-agents.git
-The `--branch latest_release` option will switch to the tag of the latest stable
+The `--branch release_1` option will switch to the tag of the latest stable
 release. Omitting that will get the `master` branch which is potentially
 unstable.
 

docs/Installation.md

 packages can be installed directly from PyPi - a Python package registry).
 
 ```sh
-git clone --branch latest_release https://github.com/Unity-Technologies/ml-agents.git
+git clone --branch release_1 https://github.com/Unity-Technologies/ml-agents.git
-The `--branch latest_release` option will switch to the tag of the latest stable release.
+The `--branch release_1` option will switch to the tag of the latest stable release.
 Omitting that will get the `master` branch which is potentially unstable.
 
 ### Install the `com.unity.ml-agents` Unity package

docs/Training-on-Amazon-Web-Service.md

 2. Clone the ML-Agents repo and install the required Python packages
 
    ```sh
-   git clone --branch latest_release https://github.com/Unity-Technologies/ml-agents.git
+   git clone --branch release_1 https://github.com/Unity-Technologies/ml-agents.git
    cd ml-agents/ml-agents/
    pip3 install -e .
    ```