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
* See the {@link ElementDefn}class for more information on metadata, including
 * the use of the metadata definition file.
 * <p>
 * Members and classes in the meta-data system include:
 * <p>
 * <ul>
 * <li>The {@link #getDefn}method gets the element meta-data.</li>
 * <li>The {@link #getPropertyDefn}method gets the meta-data for a system- or
 * user-defined property.</li>
 * <li>The {@link #validatePropertyValue}method validates a property value
 * using the rules defined in the meta-data for the * property.</li>
 * <li>The {@link ElementDefn}class provides the meta-data for an element
 * type.</li>
 * <li>The {@link ElementPropertyDefn}class provides meta-data for a property.
 * It has two subclasses:
 * {@link org.eclipse.birt.report.model.metadata.SystemPropertyDefn}for
 * built-in properties defined in the meta-data file, and
 * {@link UserPropertyDefn}for user-defined properties.</li>
 * <li>The {@link org.eclipse.birt.report.model.metadata.MetaDataDictionary}
 * singleton class provides information to the meta-data for all elements.</li>
 * </ul>
 * 
 * <h3>Styles</h3>
 * 
 * Many elements have an associated style. Style influence the set of system-
 * defined properties, as described below. They also affect the notification
 * system as described below.
 * <p>
 * This abstract base class provides style support in the handling of property
 * values, notifications and the like. Derived classes add logic to define a