Autoconfigure backend

[retog]

As an optional behavior the proxy should put a file structure to the backend, replacing a placeholder with the name of the host used to access the proxy on the first request.

Rationale: this allows to do an initial configuration when multiple transformer factories are shipped as vm or docker alongside the proxy.

[retog]

I think this should not be the business of the proxy, rather a simple js-app should be provided to do the initial configuration.

[retog]

reverted (misslabeled) ad0fa70 2866c6a
Closing as WONT-FIX