STM32L475VG-DISCOVERY-IOT : add general demo

First demo on STM32L475VG-DISCOVERY-IOT board.
Demo is using those components :
   * Low energy Bluetooth (SPBTLE_RF)
   * temperature and pressure sensor (LPS22HB)
   * temperature and humidity sensor (HTS221)
   * Time Of Flight sensor (VL53L0X)

Author: VVESTM

README.md

@@ -1,2 +1,10 @@
 # STM32Examples
 Provides several examples for the Arduino core for STM32 MCUs.
+For the complete description of each example, please refer to the comments at the beginning of each .ino file.
+
+Examples for STM32L475VG-DISCOVERY board :
+  * BTLE_sensors_tof_demo.ino :
+	* get environmental data and send it via  BlueTooth to your smartphone.
+	* use Time of Flight sensor to detect gestures
+
+Feel free to share your examples...