Bug 153040 Template definition should be removed after the report item is deleted
Steps to reproduce: 1.New a report, extends lib.label 2.Convert the label to template report item, and revert it back to the report item 3.Delete the label 4.Remove the included library Expected result: Library can be removed Actual result: A BIRT exception occurred. Plug-in Provider:Eclipse.org Plug-in Name:BIRT Model Plug-in ID:org.eclipse.birt.report.model Version:2.1.0.v20060808-0630 Error Code:Error.LibraryException.LIBRARY_HAS_DESCENDENTS Error Message:The library "Lib" can no be dropped because it has descendents "NewLabel" in the current module.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/metadata/MetaDataDictionary.java
* Validates that an element name is valid. Throws an exception if the name
	 * is not valid.
	 * 
	 * @param name
	 *            the element name to validate
	 * @throws MetaDataException
	 *             if the name is not valid
	 */
	private void validateElement( String name ) throws MetaDataException
	{
		if ( getElement( name ) == null )
			throw new MetaDataException( new String[]{name},
					MetaDataException.DESIGN_EXCEPTION_ELEMENT_NAME_CONST );
	}
	/**
	 * Builds the list of property types.
	 */
	private void buildPropertyTypes( )
	{
		
		for ( int i = 0; i < propertyTypes.length; i++ )
			propertyTypes[i].build( );
	}
	/**
	 * Builds the list of element definitions.
	 * 
	 * @throws MetaDataException
	 *             if the build of the element definition fails.
	 */
	private void buildElementDefinitions( ) throws MetaDataException