%-encoded characters in the ToC cause navigation issue

[llemeurfr]

sample-with-comma.epub.zip

In the testapp, go to the ToC, try jumping to "section2 comma" -> ok; jump to "section1"; try jumping to "section2 encoded comma" or try jumping to "section' encoded space" -> KO.

%-encoded characters in paths are not correctly handled here, but are correctly handled when found in the manifest (content.opf).

[mickael-menu]

This issue from @ryan-w reports the same problem, with a suggested fix: https://github.com/readium/swift-toolkit/issues/94