initialization of empty quantities?
Do we really need the following else-case: (see constructor of quantity.Discrete)
if isa(valueOriginal, 'quantity.Discrete')
% allows the conversion of a quantity object without
% extra check if the object is already from class
% quantity.Discrete
obj = valueOriginal;
else
% % empty object. this is needed for instance, to create
% % quantity.Discrete([]), which is useful for creating default
% % values.
obj = quantity.Discrete.empty(size(valueOriginal));
end