Nullable bool false value valid fix

Hi,
I've tried to fix bugs related to submitting "False" string value in required field. 
First bug appears on client when you try to submit form with input containing "False" value (not a radio) you will get validation error even when you have textbox or select.
Second related to support bool? type validation. In this case "compex" type is generated instead of bool and produce client side some parse value function to fail. I've also changed RequiredIf attributes to support nullable bool validation. Unfortunately it was a pain to identify type of boxed bool? value or validated property, so I was forced to add InvalidOnFalse attribute property to be able to change and don't brake current behavior.