add constructors with reference to SPI / I2C objects

[olikraus]

This could replace the current 2nd device approach.
Also the testing for other interfaces could be removed.
It also would be more flexible.

See: rogerclarkmelbourne/Arduino_STM32#680

[Zipdox2]

As a workaround you can use this before calling u8g2.begin():

    u8x8_t *u8x8 = u8g2.getU8x8();
    u8x8->pins[U8X8_PIN_SPI_CLOCK] = CLOCK_PIN;
    u8x8->pins[U8X8_PIN_SPI_DATA] = DATA_PIN;