// (E.g.: 0.1m will rounded up to 1m.)
// This may be extended in the future if we require larger or smaller quantities.
//
// When a Quantity is parsed from a string, it will remember the type of suffix
// it had, and will use the same type again when it is serialized.
//
// Before serializing, Quantity will be put in "canonical form".
// This means that Exponent/suffix will be adjusted up or down (with a