Additional v3 support for A/V material

[saracarl]

<moved from ArchiveLabs/iiif.archivelab.org#77 Go read that one for the full history; I'm just capturing what's left to discuss or implement here.>

I believe that the current version of the gist supports everything discussed with the exception of image-based resources like thumbnails and accompanying canvases.

Still to do:

• Canvases should get Accompanying Canvas containing the waveforms. (And those waveforms can be served via Canteloupe)
• Add spectrogram to seeAlso
• Add thumbnails, see Should thumbnails be based on __ia_thumb.jpg or another image? ArchiveLabs/iiif.archivelab.org#97

All three of these should be evaluated for video, which is likely to be different from our audio test item.

[glenrobson]

Example item:

https://iiif.archive.org/iiif/3/hhfbc-cyl26/manifest.json