if incoming json-ld has http://iiif.io/api/presentation/2/context.json as context, substitute inline to avoid hammering server
add rdf-iiif gem dependency and test to ensure iiif painting motivation works in ldp_creator
add test for IIIF context for ContentAsText
add test for IIIF context for external URI with additional properties
Merge pull request #92 from sul-dlss/iiif

add IIIF context for incoming create requests