writerfilter: unused include

Change-Id: Ibde8c193c9558b297e7afe71cd87390143b6f25b
DOCX filter: handle decimal number format with no level text correctly

The first problem was that no level text means no list text in Word, but
Writer only does that for the "none" numbering format.

Also, when the numbering format is "none", then Writer doesn't show the
follow character (typically a tab), either, but Word does: add a zero
width space as a suffix to mimic the Word behavior on DOCX import.

Adapt CppunitTest_sw_rtfimport accordingly, that effectively tested that
LabelFollowedBy is lost on import.

Change-Id: I7d5c7e62ba3d02da4a750ba5afad07e68b0b8c38