DOCX export: put either hints or the para attr set into the para marker props

Commit d72237741ed1d8f976032ff2ee5d2a8702d3380e (abi#9930
DocxAttributeOutput::AddToAttrList: avoid duplicated attributes,
2014-11-02) added a quick fix to avoid writing duplicated attributes,
but the validation problem of duplicated elements remained.

Make sure that when writing paragraph marker properties, then we write
either the hints at the end of the paragraph or the character attributes
range of the paragraph properties, but not both.

The only exception is the character style that's always set as
a hint, as explained in commit 4bb872b1924453f22e90bdd14e2898a3e66d5551
(DOCX export: fix handling of paragraph mark on empty paragraphs,
2014-10-17).

Change-Id: I494e5bb9871aa535532fef32bd344d8093e9f762