- ResolvableTraits: Renamed the 'const ResolvableTraits::KindType _kind'

- ResolvableTraits: Renamed the 'const ResolvableTraits::KindType _kind'
  to 'kind'. Pubic available constant values should not start with an
  '_'.

- Edition: Added 'static const Edition Edition::noedition;'. Constant
  representing 'no Edition' or 'empty Edition', as you like it. That's
  the Edition value the default ctor creates, or which would be prased
  from an empty string.