Add webdav support

Provide content via webdav so you can mount/map remotely, with navigation/directories like upnp/dnla clients see. This could also support transcoding, even on the fly, potentially.

I have used Milton in the past for this and it works well: http://milton.io/ It also is apache2 licensed for the community version (no locking support) and that will be enough for the read-only support needed.

I am happy to do the work since I want it, if that would help.