Release 0.138.0

Defect fix:

• Fixes issue in csv_parser parsing a CSV file with mapping_kind::m_columns,
  when parsing a quoted string containing a numeric value, processing it as a
  number rather than as a string.

Changes:

• It is no longer neccessay to place a semicolon after JSONCONS_TYPE_TRAITS_FRIEND

Enhancements:

• New convenience macro to master for generating json_type_traits for polymorphic types,
  based on the presence of properties,

JSONCONS_POLYMORPHIC_TRAITS_DECL(base_class_name,derived_class_name0,derived_class_name1,...) 

• The convenience macros JSONCONS_MEMBER_TRAITS_DECL, JSONCONS_STRICT_MEMBER_TRAITS_DECL,
  JSONCONS_TPL_MEMBER_TRAITS_DECL, JSONCONS_TPL_STRICT_MEMBER_TRAITS_DECL,
  JSONCONS_MEMBER_TRAITS_NAMED_DECL, JSONCONS_STRICT_MEMBER_TRAITS_NAMED_DECL,
  JSONCONS_TPL_MEMBER_TRAITS_NAMED_DECL, and JSONCONS_TPL_STRICT_MEMBER_TRAITS_NAMED_DECL
  now allow you to have const or static const data members that are serialized.

• basic_csv_encoder now supports json values that map to multi-valued fields and
  json objects where each member is a name-array pair.

• basic_csv_parser and basic_csv_encoder now support nan, infinity,
  and minus infinity substitution

Deprecated basic_csv_options functions removed:

• basic_csv_options& column_names(const std::vector<string_type>&)
• basic_csv_options& column_defaults(const std::vector<string_type>& value)
• column_types(const std::vector<string_type>& value)
  (Instead, use the versions that take comma-delimited strings)