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.
Why not using `!_excludedValidationTypes.Any(t => t.IsAssignableFrom(type))`?

On a side note, you should maybe add a comment on `MvcOptions.ExcludedValidationTypes` to indicate that types implementing or deriving from the registered types will also be excluded. You could also consider replacing this list approach by a more flexible filter delegate.