Issue #1206 - DefaultBodyModelValidator throws if get accessor throws.

Issue #1206
Fix: Introducing ExcludedValidationTypes in MvcOptions so that the user can exclude types which throw during Validation.
Kiran, I just checked this. The idea here is that it only does ShallowValidate for Developer type and does not recurse further. It does flow through this path and the validator is the one who sets the ModelState here.