Don't use HTTP(s) scheme when specifying a lightwalletd server

[AArnott]

I'm not certain of this, but it certainly appears that the lightwalletd protocol used between the lite wallet and server is not in fact HTTP at all. If that's the case, we should not be representing the built-in lightwalletd servers or accepting custom ones as user input with a HTTP or HTTP scheme in the front as that's extremely misleading. A simple host name and port number (and a checkbox indicating whether TLS is in use perhaps) would suffice if no scheme has been defined for it.