Add alternative Vivliostyle ePub viewer

[anjackson]

The Vivliostyle ePub viewer is quite sophisticated and could be used to improve access to ePub documents )in the short term at least, augmenting #85). See this example.

However, there have been some problems integrating it.

• When using the PyWB redirect to the viewer, the encoded URL fragment is not recognized as an absolute URL, so gets appended to the current page, so does not work (404).
• If this is fixed manually, the viewer cannot follow the redirects to the (very complicated) AWS S3 URL. Perhaps it's not suited to dealing with URLs with many query parameters?

It's still worth exploring, as perhaps redirects could be used to fix the first problem, and perhaps the latter will not crop up because the ARK URLs are simple (and also proxied behind the ePub streamer).

[anjackson]

I was able to render some pages using URLs like:

http://dev1.n45.wa.bl.uk:8209/static/viewers/vivliostyle/viewer/index.html#src=http://dev1.n45.wa.bl.uk:8209/doc/20130401000000ir_///doc-streamer%3A8000/ark%3A/81055/vdc_100040361719.0x000001/

This viewer has the opposite problem in that it seems a bit too complex. e.g. it allows book mode to be switch off, but we absolutely need that.

Also, it's not clear if I'm managing to circumvent the single-concurrent-use lock here?

[anjackson]

Not pursuing this for now.