Add support for Zoomify image base layer

[krdyke]

I added this feature to address a local need (cc @jschell42), but thought it was worth seeing if you all would be interested. My rationale for its inclusion is that it would be another, fairly easy route to work with a static, non-georeferenced image, with a major advantage over static images in that you have the speed of tiling. As I'm sure you're aware, for scanned historical maps, it frequently is the case that they don't respond well to georeferencing and are best handled outside of a web map environment. However, for detailed maps, the use of a single, static image can sometimes be pretty slow.

In the exhibit form, I added options for the Zoomify base URL, as well as the image width and height, which are included in the ImageProperties.xml file for any Zoomify-ed image. See the included image.

For a working example, see http://omeka.kevinrdyke.com/neatline/show/zoomify

Thanks!

[jamiefolsom]

Hi @jeremyboggs! I believe a fix for the issue this PR addressed was made is in #433, and that that PR supersedes this one. Is that correct, @akstuhl? If so, should we contact @krdyke and close this PR? Thanks!

[akstuhl]

Hi @jamiefolsom - #433 rebased and extended a different PR (also submitted by @krdyke) that has since been closed. It didn't address support for the Zoomify layer type, which is the focus of this PR. Would it make sense to open a new issue to review usefulness of Zoomify support to the main fork? If that becomes a priority, this PR could then be similarly updated to the current code base.

[jamiefolsom]

Ah, right you are, @akstuhl -- my mistake! I like the idea of a zoomable base image, but I think that's likely something we won't undertake on 2.6.x, since we're aiming to introduce only fixes for now. Fine to leave this as-is, until we confirm that direction. Thanks!

[akstuhl]

Agreed, thanks @jamiefolsom