Merge remote-tracking branch 'dzb/dzb' into dzb

Conflicts:
	css/viewer.css
	epub_content/epub_library.json
	lib/ReaderSettingsDialog.js
Merge branch 'dzb' into feature/metadata_modal
Merge branch 'dzb' of https://github.com/GermanCentralLibraryForTheBlind/readium-js-viewer into dzb3