* Porting Hidden and HiddenFor unit tests

Partial fix to #453
please add one test showing combination of a successful `ModelStateDictionary` lookup (like this one) with `HtmlFieldPrefix != null`.  e.g. `m => m.Property1` while `HtmlFieldPrefix == "MyPrefix"` and `Model.Property1 == "some-value"` will use `ModelStateDictionary["MyPrefix.Property1"]` entry.