[readme] Update with OCPP2.X features

Author: c-jimenez

README.md

@@ -23,6 +23,7 @@ As such it can be used and distributed in any commercial and non-commercial prod
   - [License](#license)
   - [Table of contents](#table-of-contents)
   - [Features](#features)
+  - [Branches and version management](#branches-and-version-management)
   - [Build](#build)
     - [Pre-requisites](#pre-requisites)
     - [Build options](#build-options)
@@ -41,6 +42,19 @@ As such it can be used and distributed in any commercial and non-commercial prod
 * [OCPP 1.6 features](./README_ocpp16.md)
 * [OCPP 2.0.1 features](./README_ocpp20.md)
 
+## Branches and version management
+
+The development of the OCPP 2.X.Y features has introduced a breaking change in the API and namespaces, so there are now 2 development branches:
+
+* The **develop** branch is now dedicated to the implementation of the OCPP 2.X.Y features and to bug fixes on the OCPP 1.6 features using the new API and namespaces
+* The **develop16** branch is dedicated for maintenance of the legacy OCPP 1.6 features and will only be used for bug fixing (backports from **develop** branch)
+
+The new **Open OCPP** releases created from the **develop** branch will have a version number **2.X.Y** starting with the **2.0.0** release.
+
+The legacy **Open OCPP** releases created from the **develop16** branch will have a version number **1.X.Y** starting with the **1.6.0** release.
+
+So if you are already working with **Open OCPP** without having any intention to migrate to the new API or to use the OCPP 2.X.Y features, you can keep following the **1.X.Y** releases. All the OCPP1.6 bug fixes will be backported on these releases.
+
 ## Build
 
 ### Pre-requisites

README_ocpp20.md

@@ -1,5 +1,7 @@
 # Open OCPP 2.0.1
 
+**Work in progress, we welcome any new contributor!**
+
 ## Table of contents
 
 - [Open OCPP 2.0.1](#open-ocpp-2.0.1)
@@ -8,4 +10,20 @@
 
 ## Features
 
-**TODO**
+**Open OCPP** is composed of the 4 layers defined by the protocol :
+
+* Websockets (Client or Server)
+* OCPP-J RPC
+* JSON messages serialization/deserialization
+* OCPP role (Charge Point, Central System or Local Controller)
+
+As of this version :
+
+* All the messages defined in the OCPP 2.0.1 protocol have been implemented (automatic generation from the JSON schemas provided by the OCA)
+* A JSON based device model has been implemented
+* The following roles have been implemented:
+    * Charge Point
+    * Central System
+    * Local Controller
+
+No behavior has been implemented yet for these roles, the user application will have to implement behaviors in the callbacks provided by the **Open OCPP** stack.