Support for DTBook 1.1.0 when converting epub to DTBook

We have inserted an option in the step Nordic EPUB3 to DTBook to convert to DTBook 1.1.0 (used by Nota) which is set to true as default (default is DTBook 2005). The actual conversion is executed by a stylesheet from DTBook 2005 to DTBook 1.1.0.
These changes only works when pull from jostein https://github.com/daisy/pipeline-scripts/pull/63 is merged into dtbook-validator.

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