Allow ShinySDR to function behind a reverse proxy

[thefinn93]

I wanted ShinySDR behind a reverse proxy, and ended up finding some fun stuff with the way it determines the websocket URL. Not sure if you want to accept this, but I figured I'd submit it anyway.

This change basically causes it to set the websocket URI to ws<s>://<host>/websocket/<path> if document.location.port is undefined, as it is when the page is loaded on the default port (80 for http, 443 for https). I put the following in my Apache vhost to make the reverse proxying happen, if you'd like to add it to some documentation somewhere:

        RewriteEngine On
        RewriteCond            %{REQUEST_URI}   ^/websocket             [NC]
        RewriteRule             /websocket/(.*) ws://localhost:8101/$1  [P,L]

        ProxyPass               /               http://127.0.0.1:8100/
        ProxyPassReverse        /               http://127.0.0.1:8100/

Also, sorry, my editor appears to have removed all tailing whitespace on every line in the file, which makes the diff look weird. The relevant changes start on line 216.

[kpreid]

I entirely approve of making reverse proxying work better, but this particular change is making the wrong thing the code currently does worse. The right thing is as commented:

// TODO: Have server deliver websocket URL, remove port number requirement

That is, the info delivered to the client (in index.template.xhtml) should include the full ws://... URL to connect to, and the client should use that URL. The client should not, as it currently does, be constructing URLs according to hardcoded rules.

Since you've pointed out a good reason to fix this, I'll probably get to it sooner.

In the even bigger picture, really I ought to drop txWS in favor of something that lets us use a single port. (I've got an experimental branch that uses Autobahn instead, but it doesn't work completely.)

[kpreid]

As of commit 5dfb897, the WebSocket URLs are provided by the server instead of derived by the client.

The remaining element of fixing this “correctly” is to provide a configuration option to change the generated URLs.

[kpreid]

Closing this pull request (per above explanation) in favor of #92 to track the remaining work (changing the generated URLs).