OPENNLP-1792: Add docbkx plugin config to produce PDF of dev manual

[mawiesne]

What does this PR do?

OPENNLP-1792: Add docbkx plugin config to produce PDF of dev manual

• modernizes xml files of the OpenNLP dev manual to use Docbook dtd in version 5.x
• adds plugin configuration to produce the PDF as separate outcome
• adds xsl file for customization of the layout of text in the PDF
• adds hyphenation support for PDF version
• introduces specific profiles for html, pdf, and epub3 targets of the dev manual
• fixes inconsistencies in dev manual's structure (duplicate ids...)
• fixes 'informaltable' column counts, mainly in cli.xml
• fixes missing inlinemediaobject for parsetree1.png image include causing trouble during epub3 generation
• adds config for pdf and epub file inclusion to bin.xml config in opennlp-distr/assembly

How to reproduce on local machine

• switch to the branch related to this PR
• cd opennlp-docs
• mvn clean verify -Pdocs-manual-html -Pdocs-manual-pdf -Pdocs-manual-epub
• inspect target/docbkx for sub directories pdf, html, and separate opennlp.epub file.
• enjoy and provide feedback

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[mawiesne]

Note: I ran checks for the resulting epub file (German output)

Mac:docbkx mwiesner$ epubcheck opennlp.epub
Verwendung der EPUB 3.3 Prüfungen
Das EPUB enthält keine Fehler oder Warnungen.
Es ist valide.
Meldungen: 0 Schwerwiegende Fehler / 0 Fehler / 0 Warnungen / 0 Informationen

EPUBCheck abgeschlossen

So it seems, epubcheck is telling us, we create a valid EBook for the OpenNLP dev manual, including a cover image.

[atarora]

Looks good !
Thanks !