Update version numbers and changelog for release 3 branch (#4076)

com.unity.ml-agents/CHANGELOG.md

 and this project adheres to
 [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
-## [Unreleased]
-
-### Major Changes
-#### com.unity.ml-agents (C#)
-#### ml-agents / ml-agents-envs / gym-unity (Python)
-
-### Minor Changes
-#### com.unity.ml-agents (C#)
-#### ml-agents / ml-agents-envs / gym-unity (Python)
-
-### Bug Fixes
-#### com.unity.ml-agents (C#)
-#### ml-agents / ml-agents-envs / gym-unity (Python)
-
 ## [1.1.0-preview] - 2020-06-10
 ### Major Changes
 #### com.unity.ml-agents (C#)

com.unity.ml-agents/Runtime/Academy.cs

         /// Unity package version of com.unity.ml-agents.
         /// This must match the version string in package.json and is checked in a unit test.
         /// </summary>
-        internal const string k_PackageVersion = "1.0.2-preview";
+        internal const string k_PackageVersion = "1.1.0-preview";
 
         const int k_EditorTrainingPort = 5004;
 

com.unity.ml-agents/package.json

 {
   "name": "com.unity.ml-agents",
   "displayName": "ML Agents",
-  "version": "1.0.2-preview",
+  "version": "1.1.0-preview",
   "unity": "2018.4",
   "description": "Use state-of-the-art machine learning to create intelligent character behaviors in any Unity environment (games, robotics, film, etc.).",
   "dependencies": {

gym-unity/gym_unity/__init__.py

 # Version of the library that will be used to upload to pypi
-__version__ = "0.17.0.dev0"
+__version__ = "0.17.0"
-__release_tag__ = None
+__release_tag__ = "release_3"

ml-agents-envs/mlagents_envs/__init__.py

 # Version of the library that will be used to upload to pypi
-__version__ = "0.17.0.dev0"
+__version__ = "0.17.0"
-__release_tag__ = None
+__release_tag__ = "release_3"

ml-agents/mlagents/trainers/__init__.py

 # Version of the library that will be used to upload to pypi
-__version__ = "0.17.0.dev0"
+__version__ = "0.17.0"
-__release_tag__ = None
+__release_tag__ = "release_3"