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/validators/ElementExtendsValidator.java
{
	/**
	 * Name of this validator.
	 */
	public final static String NAME = "ElementExtendsValidator"; 
	/**
	 * The singleton instance of the validator.
	 */
	protected final static ElementExtendsValidator instance = new ElementExtendsValidator( );
	/**
	 * Returns the singleton validator instance.