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
* Finds a theme in this module and its included modules.
	 * 
	 * @param name
	 *            Name of the style to find.
	 * @return The style, or null if the style is not found.
	 */
	public Theme findTheme( String name )
	{
		return (Theme) resolveElement( name, null, MetaDataDictionary
				.getInstance( ).getElement( ReportDesignConstants.THEME_ITEM ) );
	}
	/**
	 * Returns the theme of the report design/library.
	 * 
	 * @return the theme of the report design/library
	 */
	public Theme getTheme( )
	{
		if ( theme == null )
			return null;
		return (Theme) theme.getElement( );
	}
	/**
	 * Gets the name of the referenced theme on this element.
	 * 
	 * @return theme name. null if the theme is not defined on the element.
	 */
	public String getThemeName( )
	{
		if ( theme == null )