add service mesh, tracing, grayscale release screenshots, add 2.0.2 release icon

Signed-off-by: N周鹏飞@yunify <pengfeizhou@yunify.com>

README.md

 # KubeSphere
 [![License](http://img.shields.io/badge/license-apache%20v2-blue.svg)](https://github.com/KubeSphere/KubeSphere/blob/master/LICENSE)
 [![Build Status](https://travis-ci.org/kubesphere/kubesphere.svg?branch=master)](https://travis-ci.org/kubesphere/kubesphere)
+[![KubeSphere release](https://img.shields.io/github/release/kubesphere/kubesphere.svg?color=release&label=release&logo=release&logoColor=release)](https://github.com/kubesphere/kubesphere/releases/tag/advanced-2.0.2)
 
 ![logo](docs/images/kubesphere-logo.png)
 

docs/screenshots.md

@@ -24,6 +24,26 @@ Screenshots of various KubeSphere dashboard views:
 
 ![](https://pek3b.qingstor.com/kubesphere-docs/png/20190710113153.png)
 
+## Service Mesh
+
+### Traffic Management
+
+![](https://pek3b.qingstor.com/kubesphere-docs/png/20190713002111.png)
+
+![](https://pek3b.qingstor.com/kubesphere-docs/png/20190713002849.png)
+
+### Tracing
+
+![](https://pek3b.qingstor.com/kubesphere-docs/png/20190713002331.png)
+
+![](https://pek3b.qingstor.com/kubesphere-docs/png/20190713002424.png)
+
+## Grayscale Release
+
+![](https://pek3b.qingstor.com/kubesphere-docs/png/20190713002554.png)
+
+![](https://pek3b.qingstor.com/kubesphere-docs/png/20190713002641.png)
+
 ## Node Management
 
 ![](https://pek3b.qingstor.com/kubesphere-docs/png/20190710111701.png)