Add BLE and WiFi Example Guides (#8)

* Add BLE and WiFi Example Guides

* BLE

- BLE Battery Client
- BLE Battery Service
- BLE Beacon
- BLE Scan
- BLE UART Client
- BLE UART Service
- DHT over BLE UART
- Door Unlock Over BLE Uart
- HID Gamepad
- HID Keyboard
- HID Mouse
- PWM over BLE UART
- V7RC Car With Video Streaming
- WiFi Config Service

* WiFi

- Calculate UDP Receive Delay
- Calculate UDP Receive Timeout
- Calculate UDP Sending Delay
- Concurrent Mode
- Connect to WiFi
- Create WiFi AP
- Scan Networks
- Simple Http Request to Retrieve Webs
- Simple Http Server to Control LED
- Simple Http Server to Receive Data
- Simple TCP Server
- Simple UDP
- SSL Client for HTTPS Communication

* Update Simple HTTP Server to Control LED.rst

* minor bug fix for image path

* Delete Video API bak files

* delete video bak files (similar to multimedia API)

* Moved Arduino-build-in Example Guide

* place Arduino-build-in Example Guide under _common folder

Author: kevinlookl