Undo strict tile caching
Undo strict tile caching

Turns out caching the Open Seadragon requests for the initial thumbnails
is very valuable on huge images.  Who could possibly have guessed such a
crazy and unexpected thing could be?!?

e.g., OSD makes requests for "50," (50 x 0, essentially) followed by
"100,", "200,", etc.  These requests are very expensive on JP2 files,
and they all fire off pretty much immediately.

Unfortunately this means that all simple thumbnails are liable to be
cached, but that seems like a necessary evil.

uoregon-libraries/rais-image-server,uoregon-libraries/rais-image-server,uoregon-libraries/rais-image-server,uoregon-libraries/rais-image-server