Reads analog signal value from ADC port. Does not check if port is a valid analog port. Arduino Unos with DIP ICs typically only have six analog ports broken out to headers: A0-A5. SMD Unos (such as the Grove Beginner Kit) also have headers for ports A6 and A7, however the function isValidAnalogPort does not consider A6 and A7 to be valid ports and so the inbuilt analog-read node cannot be used with these ports. This library provides an alternative analog-read node which doesn't check if the analog port is valid.