Issue 3735: misbehaving tag sets
Issue 3304: expire chapter header when work authorship is updated
Merge pull request #1307 from elzj/issue_3304_chapter_header_caching

Issue 3304: expire chapter header when work authorship is updated
Merge pull request #1306 from CristinaRO/098-issue-3735-tagsets-misbehave

Issue 3735: misbehaving tag sets