Normalized way for multiple sensor magnitudes

[maxpowel]

Hi! This library is very nice! But an event can't contain multiple values (because it is an union) neither the interface offers a way to provide them. I was checking some libraries for sensors to see how do you deal with that and I saw the following:
In DHT you handle this doing dht.temperature().getSensor(&sensor);
And in BMP183 you get the event and then bmp.getTemperature();

As you can see you handle this by two different ways and I think that a normalized way to do this would be great. I am doing a library that needs sensors as much generic as possible and at this moment I can't use sensors as "generic" sensor when the sensor provides multiple values.

Thank you!