Update to 0.17
    
    - Update to 0.17
      - Fix RT#46473: license url with fragment part
      - Fix RT#47393: "optional_features" as map rather than list
      - Renamed word() to keyword()
      - Added identifier() validation
      - Changed optional_features key from a keyword to an identifier type
      - Clarified spec defined and user defined keys
      - Fixed qr// delimiters due to issues with the NOT SIGN symbol