Add support for 'current_date' as a default parameter

[rafrombrc]

It's possible to use static values as default parameter values in queries, but we have a need to use predefined variables such as 'current_date' as well.

[washort]

Since parameters are just done by string substitution, you can just put now() or any other SQL expression as a value for a parameter.

[arikfr]

Brilliant :)

One downside: you can't use the date picker in this case.

[rafrombrc]

@davismtl Does this solution (i.e. using now() as the default parameter) satisfy the use case that you're interested in?

[davismtl]

Yeah, I think it'll resolve a lot!