Create a W3C WebPub Manifest parser

[llemeurfr]

This will allow the import of packaged or streamed audiobooks when they are formatted using the audiobooks W3C format.

The W3C WP Manifest is a sibling of the Readium WP Manifest. The main difference is that the W3C WPM expressed a ToC via an HTML resources, where a RWPM expresses it via a JSON structure inside the manifest. The parser must therefore translate the HTML Toc to a machine readable ToC. Note that this is a general mechanism for RWPM, as indicated in https://github.com/readium/webpub-manifest#6-table-of-contents.