[2.2][Form] Add bind method to the FormInterface

| Q             | A
| ------------- | ---
| Bug fix?      | in a way
| New feature?  | no
| BC breaks?    | I don't think so
| Deprecations? | no
| Tests pass?   | yes
| License       | MIT

In the ```Symfony\Component\Form\Form``` class the method ```bind``` inherits its doc  from the implemented interface ```Symfony\Component\Form\FormInterface``` where this method does not exist.
See https://github.com/symfony/symfony/blob/2.2/src/Symfony/Component/Form/Form.php#L501.

Furthermore, the now deprecated method ```bindRequest``` refers to the method ```bind``` of the same name of the ```Symfony\Component\Form\FormConfigInterface``` which does not contain this method either. And I think it should be ```FormInterface``` instead of ```FormConfigInterface```.
See https://github.com/symfony/symfony/blob/2.2/src/Symfony/Component/Form/Form.php#L652.