The LTC2991 only supports single ended voltage measurements

It seems that I need differential measurement support. To make things easy and quick I would

• add three new parameters to AKI2CLTC2991Configure() for the three control registers
• rename convertToVoltage() to convertToSingleEndedVoltage()
• add convertToDifferentialVoltage()
• maybe add convertToCurrent()?
• use the value of the control registers to determine which conversions need to be done

Is this okay for you @hinkokocevar?