- change write(const string&) to write(const std::string&).
This allows output of std::string without an intermediate copy.
- additional writeQuoted method to handle range of char data:
writeQuoted(const char* str, std::streamsize len, bool)
This helps with supporting string_view and span<char>
- add operator<< for stdFoam::span<char> and std::string_view (c++17)
- avoid duplicate code in OBJstream
STYLE: add override keyword for IO stream methods
