SV-Zanshin/BME680: Enhancements and Bug Fixes

A new example program, SDLoggerSPIDemo.ino has been added and the following bugs/enhancements have been incorporated into this release:

12 - First measurment after power-up is incorrect 14 - Sporadic problems when reading humidity and pressure 15 - Oversampling setting for pressure and temperature switched 16 - reset() function when using I2C specific address in begin() not working correctly 17 - modified "getOversampling()" to also return current setting without changing value