Allow Dynamic injection of GlobalDisclaimer from URL

[whatnick]

Currently GlobalDisclaimer.html is webpacked into index.js and cannot be overridden at runtime without recompiling a custom image. A client configuration variable such as globalDisclaimer.dynamic can be used to allow loading the disclaimer text dynamically via the require or fetch API.

          if (
            defined(globalDisclaimer.dynamic)
          ) {
            var protocol = window.location.protocol;
            message += require(protocol + "//" + hostname + "/GlobalDisclaimer.html");
          }
          else {
            message += require("./lib/Views/GlobalDisclaimer.html");
          }