Small change to support StopOnFirstFailure between rule chains

So I'm not too familiar with this code base and my change feels a bit dirty (mostly don't like the naming similarity between the intra-chain cascade and the inter-chain cascade) but it clearly shows the functionality that I'm looking to achieve within FluentValidation. I find often that I'll have situations where the validation of one property requires that some other subset of properties already be proven valid. Or that the validation is non-trivial and I'd like it to bail as early as possible.