Dynamic transcoding feature

[tiefling]

I've tested this now with:
- My LG TV (Does not support DSD)
- My Denon AVR (Supports only DSD64)
- Sony UHD (I assume supports DSD up to 64 - May be wrong)

I couldn't get MinimStreamer transcoding to work in either situation.

Testing with these configurations:

`dsf:-/wav24;88, dsf(128):-/wav24;88, dsf(256):-/wav24;88`
`dsf:-/wav16;44, dsf(128):-/wav16;44, dsf(256):-/wav16;44`

The best I can get is the native DSD on my AVR - I can get the desired output fine if I remove the `-/` from the beginning, but that's back to serving the lowest common denominator again.

The Sony UHD is an odd beast and seems to regularly crash when you try to feed it Stereo so I'm not reading anything into that not playing ball.

Tested with Serento and mConnect control points. Serento only used for the DSD64 test cases due to having to be re-synced for the 128 / 256 cases, as was last synced with `dsf:-/wav24;88, dsf(128):wav24;88, dsf(256):wav24;88` so was not offering DSD from it's library.

I'll manually encode PCM variants where I don't have them (It's only about 6 albums).