The state of a PPGLayout is made up of two parts.
The first part is the list of PPGItems which define the controls
and their arrangment. The second part is the set of attributes, which is information
that applies to the page as a whole. This information is exposed via this method.
The siPPGLayoutAttribute enumeration provides a complete list
of all these attributes and their meaning.
Some of the most common attributes are also exposed directly as properties of the
PPGLayout, for example PPGLayout.Logic.
