added category 1-3 detection to epub validation
Merge pull request #228 from nlbdev/category-detection

added category 1-3 detection to epub validation
Removed nordic266a (ol in rearnotes) and updated message for nordic204c
support for the code element
Merge pull request #234 from nlbdev/code-element

Support for the HTML <pre> element
added support for DTBook 1.1.0 when converting from epub to dtbook
Merge branch 'master' of https://github.com/nlbdev/nordic-epub3-dtbook-migrator
stylesheet changes