Before this fix serve dlna was only using the built in database of
mime types to look up the mime types of files. On Android (and
possibly other systems) this is very small.
The symptoms of this problem was serve dlna only listing images and
not videos.
After this fix we use the backend's idea of the mime type if possible
which will be more accurate.
Fixes#3475
Mostly trying to get logging to happen through rclone's log methods.
Added request logging, and a trace parameter that will dump the
entire request/response for debugging when dealing with poorly
written clients.
Also added a flag to specify the device's "Friendly Name" explicitly,
and made an attempt at allowing mime types in addition to video.
Again, mostly just copying what I see in other implementations. This
does seem to have done the trick so that I can now pause, fast forward,
rewind, etc., on my Samsung F series.
