MIDI spec questions

I did some updates to the spec this morning.  We still have six open issues:

   1. Cross-platform persistent identifiers:
   https://github.com/WebAudio/web-midi-api/issues/124 - I think this
   should be solved along with VSTis and virtual MIDI ports.  I think this can
   be closed as essentially a duplicate of #45 below.
   2. MIDI input/output disconnection:
   https://github.com/WebAudio/web-midi-api/issues/79 - This is pending
   some final wrangling mostly between myself and Takashi; should be resolved
   in the next day or two.
   3. General MIDI support:
   https://github.com/WebAudio/web-midi-api/issues/110 - I would like to
   won't-fix and close this.  The only thing I could see us doing here is some
   way of the user specifying a "default General MIDI device".  As these are
   usually no longer present (Windows and OSX don't ship a default device
   anymore, IIUC), and features that require user configuration tend to almost
   never work (and the user could config it in the web app anyway), I would
   strongly suggest we won't-fix this.
   4. Web MIDI should be available from Workers:
   https://github.com/WebAudio/web-midi-api/issues/99 - I think we need to
   decide if this is critical for v1 or should simply be a future enhancement.
   5. Does MIDIPort.id need to be origin-scoped:
   https://github.com/WebAudio/web-midi-api/issues/79.  I think the answer
   to this is "no", as per outlined in issue comments.
   6. Virtual MIDI ports: https://github.com/WebAudio/web-midi-api/issues/45
   - I think we agreed at the FTF this should be v2.

As I said, I think point 2 will be worked out in the next couple of days;
the rest of these I am actively proposing resolutions for (1 resolved as a
dupe of 6, 3 and 5 won't-fixed, and 4 moved to v2.)  I would welcome input
on these issues.

-Chris