fixed select with ng:format

select (one/multiple) could not chose from a list of objects, since DOM requires string ids.
Solved by adding index formatter, which exposed incorrect handling of formatters in select
widgets.

src/JSON.js

@@ -33,7 +33,7 @@ function toJson(obj, pretty) {
  * @returns {Object|Array|Date|string|number} Deserialized thingy.
  */
 function fromJson(json, useNative) {
-  if (!json) return json;
+  if (!isString(json)) return json;
 
   var obj, p, expression;