Fix typos in imports and i18n

`app/ui.js` had an incorrect import path which caused issues
when using the ES6 and/or CommonJS builds of noVNC.

`core/util.js` had a non-strict-compatible declaration of a variable
without a `let` or `var` (it now uses `let`).

This fixes both issues.

app/ui.js

@@ -14,7 +14,7 @@
 /* [module]
  * import Util from "../core/util";
  * import KeyTable from "../core/input/keysym";
- * import keysyms from "./keysymdef";
+ * import keysyms from "../core/input/keysymdef";
  * import RFB from "../core/rfb";
  * import Display from "../core/display";
  * import WebUtil from "./webutil";

core/util.js

@@ -466,7 +466,7 @@ Util.Localisation = {
             }
 
             for (var i = 0;i < elem.childNodes.length;i++) {
-                node = elem.childNodes[i];
+                let node = elem.childNodes[i];
                 if (node.nodeType === node.ELEMENT_NODE) {
                     process(node, enabled);
                 } else if (node.nodeType === node.TEXT_NODE && enabled) {