seeInField with radio buttons

Some suggestions/questions for `seeInField`:

1. Even if not explicitly mentioned at http://codeception.com/docs/modules/WebDriver#seeInField it works for radio buttons too? And probably select's and checkbox'es too?

1. For radio buttons, you need to pass the *value* as second argument:
````
$I->seeInField('.gender', 1);
````
...which isn't very readable ;-) So I'm suggesting a method to assert a radio button's value by its *label* - something like:
````
$I->seeRadioSelected('.gender', 'female');
````

1. How can you assert that no radio button is selected? I tried `seeInField` with `null` or `''` as second argument - both didn't work. So I'm suggesting to include that too.