Add support for hosting under subpath

[wsidl]

Working on a hosting cluster with many public interfaces and multiples services, I want to be able to deploy this project with other similar projects under a shared subdomain. Each project would be assigned a subpath (for example, "https://services.example.com/links").

With the latest 1.13 release, deploying this project behind a reverse proxy causes the project to fail as all links are hardcoded to the root of the project.

Currently, the project does not take into account paths provided by the "X-Forwarded-*" headers and would greatly improve the various environments this will get deployed.