Improved the rest of the schematron messages, also changed dtbook guidelines to 2015-1

 * lists with lic's should not use bullets or numbering when converted to DTBook
 * removed references to strict schematron from test files (since there's no explicitly "strict" rules anymore)
 * renamed all tpb* error ids into nordic* ids, fixes #183
 * improved messages in epub3 schematrons, fixes #185 and fixes #128
 * changed dtbook guidelines revision from 2011-2 to 2015-1, fixes #245