Detect IIIF region parameter that represents full image

[donaldgray]

The Orchestrator has special handling for /full/ IIIF region parameter to allow for more efficient serving of images using pre-generated thumbnails or via special-server to save load on the tile handling image-server.

We should add logic to Orchestrator to detect IIIF region parameters that don't specify /full/ but the region represent the full image. The cached OrchestrationAsset contains enough information to calculate this.

Do we also need to update thumbs handler to recognise these as full, or is that already handled in calculations?

Region parameters that could represent /full/ are:

• /x,y,w,h/ format requests where x + y are 0 and w + h match those of the source image. E.g. for a 2234x5466 image this would be 0,0,2234,5466.
• /square/ format requests where the origin image is already square (Asset.Width == Asset.Height).