Support for webp

[jcoyne]

I found this comment about webp not working, however, there is lots of code in the codebase dealing with webp. Can we clarify whether webp is supported?

When I request one on my server I see:

415 Unsupported Media Type

In the log I only see:

Nov  6 08:54:29 sul-imageserver-stage-a java[1501]: 08:54:29.534 [qtp2001223946-1837] #033[34mINFO #033[0;39m #033[36me.i.l.c.r.i.v.ImageResource#033[0;39m - Handling GET /iiif/2/tq%2F566%2Fym%2F4557%2Fargo-logo.jp2/full/802,/0/default.webp
Nov  6 08:54:29 sul-imageserver-stage-a java[1501]: 08:54:29.541 [qtp2001223946-1837] #033[34mINFO #033[0;39m #033[36me.i.l.c.r.ErrorResource#033[0;39m - Handling GET /iiif/2/tq%2F566%2Fym%2F4557%2Fargo-logo.jp2/full/802,/0/default.webp