[Feature Request] Pass onvalidation dict to smartgrid

[sinaisix]

As per this thread on the forums, a smartgrid can be passed a limited set of params as dict to be passed to child grids. However, onvalidation isn't part of the params that can be passed to child grids via a dict.

This is problematic because then it means a child grid created cannot have any custom validation done, for instance, to enforce multi-column unique constraints.

I humbly request that onvalidation be part of the smartgrid params that can be passed to child tables via a dict.

[mdipierro]

Can you submit a patch for this? I will take it.