Bug 138562 Splite extendsexcpetion to seperate sub class
The suggestion is Parent invalid Cycle extends Different type extends Not top level extends
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/command/ExtendsException.java
{
	/**
	 * Comment for <code>serialVersionUID</code>.
	 */
	
	private static final long serialVersionUID = 4652036899546927124L;
	/**
	 * The new extends value.
	 */
	protected String extendsName = null;
	/**
	 * The parent element to set.
	 */
	protected DesignElement parent = null;
	/**
	 * No element exists with the parent name.
	 */
	public static final String DESIGN_EXCEPTION_NOT_FOUND = MessageConstants.EXTENDS_EXCEPTION_NOT_FOUND;