Whitelist of properties for validation

[floatdrop]

This feature can be handy when you have two objects (state before modification and after). After retrieving paths for properties that changed we could check only fields that changed with same validation as for whole object. This is also useful when object in DB are written with old version of validation, but should be modifiable with new version of validator.

[dhoepelman]

This is a bit too vague to be actionable. Would need a more clear description of the problem and/or proposed API.