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/core/DesignElement.java
{
			throw new ExtendsException( this, parent,
					ExtendsException.DESIGN_EXCEPTION_WRONG_TYPE );
		}
		else if ( parent == this )
		{
			throw new ExtendsException( this, extendsName,
					ExtendsException.DESIGN_EXCEPTION_SELF_EXTEND );
		}
		else if ( parent.isKindOf( this ) )
		{
			throw new ExtendsException( this, parent,
					ExtendsException.DESIGN_EXCEPTION_CIRCULAR );
		}
	}
	/**
	 * Gets the value of a property as an integer.
	 * 
	 * @param propName
	 *            the name of the property to get
	 * @param module
	 *            the module
	 * @return the property value as an integer. Returns 0 if the property is
	 *         not defined, or cannot convert to an integer.
	 */
	public int getIntProperty( Module module, String propName )
	{
		ElementPropertyDefn prop = getPropertyDefn( propName );
		if ( prop == null )
			return 0;