DOCX export: add method to write wp + dml markup for an SdrObject

Also, factor out common code from FlyFrameGraphic() and
WriteDMLDrawing() to lcl_startDMLAnchorInline() and
lcl_endDMLAnchorInline() to avoid code duplication.

Change-Id: Ic1bed48e45b1cdb2d061ed7099206c0b1aa4f9f7
DOCX shape export: when in experimental mode, use DML instead of VML

Change-Id: I8a07b74c047dfa2c4b1096e3cd3ace3bd5f93d0a