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
}
	/**
	 * Test for method clearProperty(String).
	 * <p>
	 * Test Cases:
	 * 
	 * <ul>
	 * <li>sets new property</li>
	 * <li>clears just added new property</li>
	 * </ul>
	 * 
	 * @throws SemanticException
	 */
	public void testSetandClearProperty( ) throws SemanticException
	{
		propertyOperate( "height", "2mm", true );
		propertyOperate( "height", null, true );
		propertyOperate( "displayName", "world", true );
		propertyOperate( "displayName", null, true );
	}
	/**
	 * Test if property handle can set and get value rightly.
	 * 
	 * @param prop
	 *            get property name from it
	 * @param value
	 *            property value
	 */
	private void PropertyDefnOperate( ElementPropertyDefn prop, Object value )
	{