Specify format for datetime placeholders

[nickynicolson]

When using placeholders like created and modified it would be useful to be able to specify a format string - I'm probably only interested in date, or datetime to minute level precision - seconds and milliseconds not usually necessary.

[jplattel]

That's a good idea, would it be nice to have this configurable through the code block? So you could say:

```oql
<other paramaters here>
dateFormat: "YYYY-MM-DD" 

Or something like that? :)

[nickynicolson]

Yes that looks like a good solution