Bug 193245 Should block user to set content type property on the child element
After we switch from the slot to content element type property, all the rules that we applied to the slot before should be applied to the content element type property. When an element is extended from the library element, it should not be allowed to change the child element structure. So, when user call setProperty() to set the value of the content element type property, Model should throw out exception.
model/org.eclipse.birt.report.model.tests/test/org/eclipse/birt/report/model/command/PropertyCommandTest.java
assertTrue( rules.size( ) == judgeType( type ) );
	}
	/**
	 * If type is false mean EmptyList ,then return 1, else return 3.
	 * 
	 * @param type
	 *            mark of size of rules is zero or not
	 * 
	 * @return the integer flag
	 */
	private int judgeType( boolean type )
	{
		if ( type )
			return 3;
		return 1;
	}
	/**
	 * Invoke
	 * {@link org.eclipse.birt.report.model.command.PropertyCommand#replaceItem( MemberRef,
	 * IStructure, IStructure)}.
	 * 
	 * <p>
	 * Test Cases:
	 * 
	 * <ul>
	 * <li>Execute the command, save the file,compare with a golden file, they
	 * should be identical</li>
	 * <li>Undo the command, save the file,compare with a golden file, should
	 * be</li>
	 * <li>Redo the command, save the file, compare with a golden file, should