Core: feature add 2FA (OTP) (#1054)

Add 2 factor authentification for improved security on your websites/apps.

Taken from TrinityCore

Closes #1049 on github.

src/server/authserver/Server/AuthSocket.h

@@ -67,6 +67,7 @@ private:
     eStatus _status;
 
     std::string _login;
+    std::string _tokenKey;
 
     // Since GetLocaleByName() is _NOT_ bijective, we have to store the locale as a string. Otherwise we can't differ
     // between enUS and enGB, which is important for the patch system