Bug 124620 Referenced Parameter icon should be invalid if the parameter in library is deleted
Description: Referenced parameter icon should be invalid if the source parameter in library is deleted. Steps to reproduce: 1.Create a library. Insert a report scalar parameter. 2.Create a report, use the above library. In the library explorer, pull the parameter to the data explorer view of report. 3.Open the library file, delete the parameter. Then reopen the report design file, the icon of parameter seems nothing happened. But if those operations happened in dataset, the icon of dataset in the report will be invalid. It is acceptable. Expected Result: The icon of referenced parameter should be invalid.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/core/DesignElement.java
* <dt><strong>By name </strong></dt>
 * <dd>Elements can have a name. Names are unique within a name space. However,
 * many elements are anonymous. Names are required only when the element will be
 * referenced. Some elements, such as styles, data sources, and data sets, exist
 * to be referenced and so require a name. Most other elements are seldom
 * referenced, and so the name is optional.</dd>
 * 
 * <dd><strong>By navigation </strong></dt>
 * <dd>Elements can be found via navigation. One can start at the module and
 * work down though the containment hierarchy. Every valid element can be
 * reached via navigation. Indeed, the definition of element creation, from the
 * perspective of the design, is when the element is added to the containment
 * hierarchy. Similarly, the definition of deletion, again from the perspective
 * of the design, is when the element is dropped from the containment hierarchy.
 * </dd>
 * 
 * <dd><strong>By pointer </strong></dt>
 * <dd>The design tool itself references elements mostly using Java pointers.
 * That is, once the application finds an element of interest, it simply holds
 * onto it using a pointer.</dd>
 * 
 * <dd><strong>By ID </strong></dt>
 * <dd>The web designer needs a simple way to reference items across calls to
 * the server. None of the above is both simple and consistent. Element IDs
 * provide this service. IDs are valid only within a single design "session". A
 * session is the time between when a design is loaded into memory, and the time
 * that the design is released. IDs are <em>not </em> valid across sessions,
 * and are not persistent. The application must enable IDs by calling
 * {@link org.eclipse.birt.report.model.metadata.MetaDataDictionary#enableElementID}.
 * Call {@link #getID}to get the ID of an element. Call