sw: move IsIgnoredCharFmtForNumbering() to SwTxtNode

I need this in SwTxtFormatter.

Change-Id: Ib1586299f468a88e92fdb367fbab69a683791dc9
SwTxtNode::IsIgnoredCharFmtForNumbering: ignore RES_CHRATR_COLOR

And also in SwTxtFormatter::NewNumberPortion(), use
SwTxtNode::IsIgnoredCharFmtForNumbering(), via
checkApplyParagraphMarkFormatToNumbering().  Otherwise the color of the
paragraph mark is inherited by the numbering portion, which is not what
IDocumentSettingAccess::APPLY_PARAGRAPH_MARK_FORMAT_TO_NUMBERING
(mirroring Word's behavior) is supposed to do.

Change-Id: I5d8df9b404916cc4a4405bf796d971ede59e6111