Mirador breaks on load when no IIIF Image support

[azaroth42]

The viewer won't start if there's a manifest that doesn't have IIIF support for every image.

Simplest possible test case: http://www.shared-canvas.org/tests/1/manifest.json

Expected behavior: A static image view without deep zoom, or preferably client side zoom ala zpr.

[regisrob]

up for this!