Plex App API config assumes exposure of TCP 32400 #631

When configuring the enhanced Plex app, Heimdall assumes that TCP 32400 is exposed to communicate with a Plex server. In many cases, folks will deploy a server, and expose it on 80/443 via a reverse proxy, so 32400 is never exposed to the internet. As the API is REST, there's no reason that we should assume 32400.

Example is visible below in my own config. I had to expose 32400 without proxying via my reverse-proxy, then configure a custom URL specifying http and :32400 to successfully connect to the PMS API.