Format `sss` for milliseconds in date filter

Continuing the theme of #1936

I suggest to add to the date filter format for milliseconds:

* `sss`: Millisecond in second, padded (000-999)

For example:

```
{{1359689000081 | 'MM/dd/yy HH:mm:ss.sss Z'}} => 02/01/13 09:23:20.081 -0600
```