Fix STM32 I2C but for 1-byte Reads.
Hacked the driver to work, but does not conform
to datasheet behavior.

The STM32 I2C drivers needs to be rewritten from scratch.
Use xpcc::SoftwareI2C in the meantime.
Add working STM32 I2C driver.
Not all tricks are fully documented yet.
Beautify code and remove much debugging helpers.
Remove busy waiting for stop condition.
Add I2C sensor example code to the STM32.
Add documentation of operation and configuration.
Merge branch 'feature/stm32_i2c_debug' into develop