context path for web and api

[mmrath]

It would be nice to have an option to expose api and web frontend on a custom path. It would be easier to proxy that way.

lets say option is base-path, the following would expose all api and web on path /devmail
--base-path /devmail

[versus]

fix on #41

[erikvanzijst]

Bump. Would be nice to get his in.

@versus added it to what looks like quite a large and unwieldy combined PR that might be less like to merge that this individual change.