figgroup content model completeness (proposed feature 13030)

Robert: (Deborah Pickett's proposal) is unchanged as she submitted, 
            except for the details of the content model. As designed, it allows 
            only notes, phrases and keyword inside. 
            The original content model was too limiting. This proposal is to add 
            <data> into <figgropu> and also to add the normal phrase and block 
            elements into <figgroup>.