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/src/org/eclipse/birt/report/model/command/PropertyCommand.java
}
		if ( element instanceof ContentElement )
		{
			if ( !( (ContentElement) element ).isLocal( ) )
			{
				ContentElementCommand attrCmd = new ContentElementCommand(
						module, element, ( (ContentElement) element )
								.getValueContainer( ) );
				attrCmd.doSetProperty( prop, value );
				return;
			}
		}
		doSetProperty( prop, value );
	}
	/**
	 * Remove template definition from module if the definition is no longer
	 * refferenced when setting
	 * <code>IDesignElementModel.REF_TEMPLATE_PARAMETER_PROP</code> null.
	 * 
	 * @param prop
	 *            should be
	 *            <code>IDesignElementModel.REF_TEMPLATE_PARAMETER_PROP</code>.
	 * @param value
	 *            should be null;
	 * @throws SemanticException
	 *             if any semantic exception is thrown.
	 */
	private void clearRefTemplateParameterProp( ElementPropertyDefn prop,
			Object value ) throws SemanticException
	{