Incorrect @context in IIIF manifests

[pbinkley]

In manifests, the main @context is wrong: current it is

"@context": "http://iiif.io/api/image/2/context.json"

It should be http://iiif.io/api/presentation/2/context.json, per the spec.

The same applies to the @context in the sequences section.

[hadro]

This has been fixed in the main @context, and partially in the sequences section, but I still see a few lingering incorrect context strings in some manifests. Will need to address this in v3 rewrite

[rwd]

@hadro the @context appears now to be https://iiif.io/api/presentation/2/context.json, but that URI should begin http://, per the spec.