Subdirectory support when using a reverse proxy

[cglindkamp]

I'm using an nginx reverse proxy to add authentication and https support. This works great, when Photato is put into the root directory. But when I put it into a subdirectory, so that it is accessible via https://example.com/photato, all links still point to the root directory, so not even the css and js files can be loaded. It would be great, if this kind of setup would be supported, either by specifying the prefix in a config file or even better autodetect the prefix/use only relative paths.