Port from Adafruit's SGP30 arduino lib(https://github.com/adafruit/Adafruit_SGP30) to use Mbed api

Dependents:   AMU_Polytech_Marseille_STM32InTheSky_01_05_2019 Sensor_SGP30 Sensor_iAQ_sgp30_bme_si7051 POCBreath_V2_smd_commercial

unknown revision 'shortlog'