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
* @return the defined image that matches, or <code>null</code> if the
	 *         image name was not found in the embedded images.
	 */
	public EmbeddedImage findImage( String imageName )
	{
		StructureDefn defn = (StructureDefn) MetaDataDictionary.getInstance( )
				.getStructure( EmbeddedImage.EMBEDDED_IMAGE_STRUCT );
		return (EmbeddedImage) StructureRefUtil.findStructure( this, defn,
				imageName );
	}
	/**
	 * Gets the property definition whose detail type is of the given structure
	 * name.
	 * 
	 * @param structureName
	 *            the structure name to search
	 * @return the property definition whose detail type is of the given
	 *         structure name, otherwise null
	 */
	public ElementPropertyDefn getReferencablePropertyDefn( String structureName )
	{
		if ( referencableProperties == null )
		{
			referencableProperties = new HashMap( );
			referencableProperties.put( ConfigVariable.CONFIG_VAR_STRUCT,
					getPropertyDefn( CONFIG_VARS_PROP ) );
			referencableProperties.put( EmbeddedImage.EMBEDDED_IMAGE_STRUCT,
					getPropertyDefn( IMAGES_PROP ) );
			referencableProperties.put( CustomColor.CUSTOM_COLOR_STRUCT,
					getPropertyDefn( COLOR_PALETTE_PROP ) );