While our customized transformation works fine for single-text TEI
files, it generates invalid EPUB documents for corpus documents –
appearently the TOC generation that forms the base for OPF and NCX
metadata does not work correctly in these cases, and it is to complex to
fix just now.

The alternate approach for sourceTypes != XML now converts the corpus to
a single TEI document with a <tei:group> for every original TEI or
teiCorpus document, and runs a mostly unmodified original EPUB
transformation on this document. This leads to surplus headings, a
suboptimal TOC and some additional content, but at least these EPUBs
validate with epubcheck now.

Item level EPUBs are OK, corpus level EPUBs seem to contain errors.

Isabella Reger authored Jan 21, 2014 and thorsten.vitt committed Jan 22, 2014

Es müssen hauptsächlich die Links im Inhaltsverzeichnis angepasst werden
(template mit mode=generateLink). Leider werden momentan einige
Html-Dateien (von solchen Seiten, die nur Zwischenüberschriften
enthalten) nicht generiert, obwohl sie in der content.opf korrekt
eingetragen sind.

Observed a strange non-reproducable bug that introduced
'?sessionId=Optional.absent()` (literally) into that pattern.

Largely refactored the code: the individual services are now based on a common
superclass for common tasks, the REST API has moved to a single class,
everything uses the same code for stylesheet caching, cache control,
response headers etc.