1315: Download button for MWW instance (iframe based)

Task-Url: https://pm.winseda.de/issues/1315

js/item/item.js

@@ -130,7 +130,10 @@ ResultItem.prototype.downloadData = function(format, model) {
 
 ResultItem.prototype.handleDownloadedData = function(data) {
 	if ( window.location !== window.parent.location ) {
-		window.parent.postMessage(window.btoa(data.pojo), '*');
+		var base64 = btoa(data.pojo.replace(/[\u00A0-\u2666]/g, function(c) {
+		    return '&#' + c.charCodeAt(0) + ';';
+		}));
+		window.parent.postMessage(base64, '*');
 	} else {
 		// For now only hardcoded xml
 		var blob = new Blob([data.pojo], {type: "application/xml"});