Updates to C++17.
- Updated to C++17.
- Changes to use the safe floating point type.
- Inlined constexpr global variables.
- Adds freestanding multiplication for the floating point type.
- Splits IO manipulation into its internal and external parts.
- Renames stream manipulators to be clearer.
- Simplifies the file name of MoneySize.
- Simplifies the file name of MoneyType.