[cstdring] add format functions for working with wstring/wchar_t
[stdstring] demise cstdstring::format and replace with stringutils::format
[cstdstring] remove CStdString::Empty and replace with std::string::clear
[cstdstring] remove IsEmpty() and replace with empty()
[cstdstring] remove FormatV and replace with StringUtils::FormatV
[cstdstring] remove Trim/TrimRight/TrimLeft and replace with StringUtils::Trim*
[cstdstring] remove ToLower/ToUpper/MakeLower/MakeUpper
[cstdstring] demise AppendFormat and replace with StringUtils::Format