refactor: 💥 basic_concepts, quantity and quantity_cast refactored

BREAKING CHANGE:  ScalableNumber renamed to QuantityValue

Resolves #107

src/include/units/quantity_point.h

@@ -37,7 +37,7 @@ namespace units {
  * @tparam U a measurement unit of the quantity point
  * @tparam Rep a type to be used to represent values of a quantity point
  */
-template<Dimension D, UnitOf<D> U, ScalableNumber Rep = double>
+template<Dimension D, UnitOf<D> U, QuantityValue Rep = double>
 class quantity_point {
 public:
   using quantity_type = quantity<D, U, Rep>;