v1.6.0 to permit sending data more than 2K

### Releases v1.6.0

1. Fix severe limitation to permit sending larger data than 2K buffer
2. Add example [ATWebServer_BigData](https://github.com/khoih-prog/ESP8266_AT_WebServer/tree/master/examples/ATWebServer_BigData) to demo how to send larger data than 2K buffer
3. Modify example [AdvancedWebServer](https://github.com/khoih-prog/ESP8266_AT_WebServer/tree/master/examples/AdvancedWebServer) to demo how to send larger data than 2K buffer
4. Add new features, such as `CORS`, etc.
5. Use `allman astyle` and add `utils`
6. Update `Packages' Patches`

Author: khoih-prog