added dimension one quantity
added #plain?, #composite? methods
added #plain?, #composite? methods. defaulting label, name to values given by Unit::List#label and Unit::List#name
added #numerator, #denominator to extract from list of units. added #label, #name methods to derive attributes from list of units
delegating default label, name for units resulting of multiplication, division and exponentiation to Units::List#label and Unit::List#name
added #add_composite_unit (explicit and dynamic through #unit_for. several refactorings
QuantityValue examples are now tied to SI loaded units
new QuantityValues only for existing / valid SI.units. Explicit and dynamic conversion to other SI.unit of the same kind
mass require