Derivative query with group by time but no aggregate function should fail parse

[pauldix]

If you do the query:

select derivative(value) from foo where time > now() - 4h group by time(1m)

That query should fail. Derivatives with a GROUP BY time clause require an aggregate function to be in the call to derivative, like this:

select derivative(first(value)) from foo where time > now() - 4h group by time(1m)

This should be validated at parse time. The error message should indicate that they can use an aggregate function inside the call to derivative, like min, max, first, last, mean, or sum.