CDAP-652: updated Spark job UI to display the collected metrics in blocks

ok, didnt know about that global. Thanks.

Please drop the `new` keyword, according to string.js docs it is not needed. Or wrap it in parens:
```
// S global variable comes from string.js
var url = (new S(path)).template({'appId': appId, 'programId': programId}).s;
```