DOCX Input: Fix incorrect numbering being generated for numbered lists in some circumstances. Fixes #1301044 [DOCX conversion of numbered list](https://bugs.launchpad.net/calibre/+bug/1301044)

Apparently, list counters are associated with abstract numbering
definitions and not numbering instances. Also add support for
startOverride.
DOCX Input: Fix para styles for numbering blocks applied via pStyle not being applied