[Feature] Allow scene without date

[ghost]

I've set up a new instance that I want to use for amateur content, and I want to be able to submit scenes without date. That constraint is enforced by the voting system so I don't think it's necessary.

[MyDirtyAccount]

This would help with all the scenes dated in 1970 as a placeholder.

[Cyb3rN3xus]

I believe there should be an instance configuration to define the required fields. This would allow for instances that do not require any fields.