writerfilter: sprm:SBkc -> ooxml:EG_SectPrContents_type

Change-Id: I6a6b73967e11a9346cd766dde9d04af63466c206
writerfilter: convert sprm:CF{Bold,BoldBi,Italic,ItalicBi}

Change-Id: Ide2116ac380fd563fa7cc9e60f46a7cc62ffc94b