Some docs update and Adding a point for building a new module from Scratch.
Some docs update and Adding a point for building a new module from Scratch.

yaweiw/azure-iot-gateway-sdk,yaweiw/azure-iot-gateway-sdk,yaweiw/azure-iot-gateway-sdk,yaweiw/azure-iot-gateway-sdk,yaweiw/azure-iot-gateway-sdk