Add support for image-only IIIF manifests

[andrisi]

The demo at tify.rocks refrers to manifest files which seems to include refrerences and metadata to all pages in one file, while the one provided by the iipimage server (example below) are much simpler and only contains just info for one image. Could you support that too? If you contact me I can provide a real URL to use, but it's also quite simple to install the above server software. Thanks a lot!

{
  "@context" : "http://iiif.io/api/image/2/context.json",
  "@id" : "https://myserver.co/iiif/?IIIF=delight.tiff",
  "protocol" : "http://iiif.io/api/image",
  "width" : 30000,
  "height" : 16927,
  "sizes" : [
     { "width" : 234, "height" : 132 },
     { "width" : 468, "height" : 264 },
     { "width" : 937, "height" : 528 },
     { "width" : 1875, "height" : 1057 },
     { "width" : 3750, "height" : 2115 }
  ],
  "tiles" : [
     { "width" : 256, "height" : 256, "scaleFactors" : [ 1, 2, 4, 8, 16, 32, 64, 128 ] }
  ],
  "profile" : [
     "http://iiif.io/api/image/2/level1.json",
     { "formats" : [ "jpg" ],
       "qualities" : [ "native","color","gray","bitonal" ],
       "supports" : ["regionByPct","regionSquare","sizeByForcedWh","sizeByWh","sizeAboveFull","rotationBy90s","mirroring"],
       "maxWidth" : 5000,
       "maxHeight" : 5000
     }
  ]
}

[t11r]

This was asked before (#85) and will probably be implemented someday. Our current priority is IIIF version 3 though, so it might take some time.