Bug 197228 Need updaet createdBy info when serialize the module
When open module, designer will pass the property map which contains the createdBy info. this info should be retained by moduleHandle and then be updated and written when doing serialization. Note if this info is null, model should not update it during serialization. This could happen for api users or third-party designer. For BIRT designer, it will guarantee this value always not null.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/core/Module.java
* throw runtime exception.
	 */
	public void setReadOnly( )
	{
		activityStack = new ReadOnlyActivityStack( );
	}
	/**
	 * Returns the module namespace. Only included library has a non-empty
	 * namespace.
	 * 
	 * @return the module namespace
	 */
	public String getNamespace( )
	{
		return null;
	}
	/**
	 * Loads css with the given css file name. This file name can be absolute or
	 * relative. If the css doesn't exist or fatal error occurs when opening
	 * css,.
	 * 
	 * @param fileName
	 *            css file name
	 * @return the loaded css
	 * @throws StyleSheetException
	 */
	public CssStyleSheet loadCss( String fileName ) throws StyleSheetException
	{
		try
		{