DOC: Improved processing of group shapes.

* Added support for the REF_WITHOUT_KEYWORD field.

* Preparing a graphic style for the draw:g element. It's required for correct positioning in case of floating object.
Wrapping and positioning attributes are not required in graphic styles of child shapes. Also the child element does
not require the draw:anchor-type and draw:z-index attributes.

* Setting draw:auto-grow-height and draw:auto-grow-width to false by default in libmso. It's absence seems to affect
the layout of floating objects. The logic to set those attributes remains a TODO!