Bug 130492 Provide a method to serialize the report with library information.
Currently, when engine generate the report document file, the document does not contain any library information. That will cause many propblem on server side. Model should provide a method to serialize the report with library information to a stream so that the generated report document can contain all information that the report need.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/core/DesignElement.java
* return the style for use by the generic mechanisms.
 * <p>
 * An element that can have a style is called a <em>styled element</em>. The
 * style affects the styled elements in three distinct ways.
 * <ol>
 * <li>The element can include some or all of the properties defined for the
 * style element. The element defines only those that make sense for that
 * element. These <em>style properties</em> appear as if they are properties
 * of the element itself.</li>
 * <li>The element can name a shared style from which to get properties.</li>
 * <li>If element does provide the value for a style property, and the element
 * does not explicitly reference a shared style, then the application will use a
 * <em>property search</em> to find a style implicitly associated with this
 * element. This is a search upward in the containment hierarchy to find either
 * 1) a shared style referenced by a container, or 2) an predefined style
 * associated with the slot or element. For example, a label in a Container in a
 * List's Header slot will use the predefined "list-header" style unless another
 * style is defined on the style or Container.</li>
 * </ol>
 * <p>
 * Members and classes in the style system include:
 * <p>
 * <ul>
 * <li>The {@link #getStyle()}method returns the associated style, if any, for
 * this element as a generic DesignElement.</li>
 * </ul>
 * 
 * <h3>Inheritance</h3>
 * 
 * User-defined elements can extend other elements, but style element is not