Support for date in configuration

```
Date based response header, like {{{Expires}}}, cannot be set right now
because of the inability to specify absolute/relative date in the
configuration. Support for the above needs to be added.
Maybe, a {{{now}}} handle can be provided which will help users configure
dates like {{{now + 3600}}} etc.
```

Original issue reported on code.google.com by `avl...@gmail.com` on 28 Jun 2009 at 4:10
