-extern std::multimap<std::string, std::string> read_key_value (std::istream& s);
-extern int get_required_int (std::multimap<std::string, std::string> const & kv, std::string k);
-extern float get_required_float (std::multimap<std::string, std::string> const & kv, std::string k);
-extern std::string get_required_string (std::multimap<std::string, std::string> const & kv, std::string k);
-extern int get_optional_int (std::multimap<std::string, std::string> const & kv, std::string k);
-extern std::string get_optional_string (std::multimap<std::string, std::string> const & kv, std::string k);