Added "type" to the node object that defines node type as basic, virtual...

..., copy, subset, or parts.  Also, added Subset structure to node object to define parent node and subset information.  Lastly, added format field to all indexes.  Currently everything defaults to type array, except for the "size" index which is dynamic.  Will soon be adding the "matrix" index type that will allow for the creation of nodes that are subsets of subset nodes of a different index type.