Correct way of handling xyzFloat structures

Version 1.2.2 is not fully compatible with former versions. Many functions like getGValues() returned xyzFloat structures. To be exact, the functions did return pointers to the structures which were created by library functions. But after returning from the functions the memory space where the structures were located can be overwritten. I have changed that by passing the xyzFloat variables by reference. See also readme.

Moreover, I have added the option to change SPI pins in case your MCU board allows that. You can pass the SPI pins when creating your ICM20948_WE object.