Fix windows install.cmd

Now it only copies sbbsexec.dll (since the .exe's take care of cleaning
up files they don't need), and it knows where sbbsexec.dll lives, even
if the .cmd is run from a different directory (or run as administrator,
which sometimes runs it from a different directory)
Init connection in serverthread instead of client

Adding terminal type detection to server thread broke websocket
connections, since the handshake didn't happen until the client thread.