[Feature] UPnP server enhancements

[Tolik]

1. UPnP server should stream media from all attached devices, not only the device where NMT apps are installed.

I installed NMT Apps on USB flash so I can only see folders Video, etc. on that flash, apparently empty.
I also have internal SATA drive with a lot of videos.
To share them I had to create symbolic link in directory /share:
Video -> /opt/sybhttpd/localhost.drives/SATA...../Video
That's not very user friendly way! And not supported, of course.

2. UPnP server should not show things like .transmission and other trash.
It should only show directories Video, Music and Photo on all attached devices. Or maybe Video*, Music* and Photo*. And maybe Downloads.

3. It would be even better to make the list of shared directories configurable.
But I don't even hope.

P.S. some UPnP servers show only folders where some media files are found. I don't like this approach. Some directories may contain media files that should not be streamed. I insist that streaming must be limited to some specific directories, either configurable or hardcoded.