Bug 119566 Support template items in page header/footer
Currently you can't create template report items inside a page header/footer. This should be fixed.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/core/DesignElement.java
* 
 * Design elements maintain a wide variety of relationships to other parts of
 * the design. An element refers to its parent element or its shared style.
 * Expressions reference elements, parameters and data set columns. Many
 * elements reference data sources or data sets.
 * <p>
 * <em>Semantic processing</em> resolves name references to the actual
 * elements or other objects. Semantic processing is done incrementally for most
 * operations. However, batch processing is needed when reading a design file
 * and for certain other operations.
 * <p>
 * Semantic processing is done by doing a depth-first traversal of the design
 * tree. Errors are gathered on the design context.
 * <p>
 * The result of semantic processing may be that the design caches a reference
 * to another element as is done in this class for the parent element and the
 * shared style. In other cases, the reference is checked and then discarded.
 * <p>
 * When a reference is cached, the system must handle the case of a reference
 * that cannot be resolved. For example, an element might use a shared style
 * defined in a template, but that shared style has been deleted from the
 * template and can no longer be resolved. In this case, we cache the name until
 * the user loads the required elements, or changes the reference to an existing
 * style. Similar rules apply to the "extends" property.
 * 
 * @see ElementDefn
 * @see DesignElementHandle
 * @see ElementPropertyDefn
 */
public abstract class DesignElement