calibredb: Allow setting fo title sort field

Fixes #1233711 [CalibreDB: title_sort is not a known field](https://bugs.launchpad.net/calibre/+bug/1233711)
DOCX Input: Handle numbering without character styles

DOCX Input: Fix erorr when converting docx files that have numbering
defined with no associated character style. Fixes #1232100 [Private bug](https://bugs.launchpad.net/calibre/+bug/1232100)