Add embed-based fTelnet

Created by: rickparrish

Hey, finally had a minute to put a proper implementation in place (the one I mentioned the other day had stuff hardcoded all over the place).

It works like the version in the stock web interface, where it tells the sysop what they need to do in order to make it work (ie set rlogin_auto_xtrn to true if it's not already, add to services.ini, etc), so hopefully it won't result in any extra support requests. If it does, feel free to say "Rick broke it" and point them my way.