Added new option to fix a little issue originated from last PR

[iquabius]

After I sent this PR, I realised a little problem:
When identical validator is used in a form scope, the form will always provide a context, because of this, it wouldn't be possible to validate a literal token, see the example.

use Zend\Form\Form;
use Zend\InputFilter\InputFilter;

$form = new Form('form');
$form->add(array(
    'name' => 'humanCheck',
    'options' => array(
        'label' => 'How much is 1 + 2?',
    ),
));

$inputFilter = new InputFilter();
$inputFilter->add(array(
    'name' => 'humanCheck',
    'required' => true,
    'validators' => array(
        array(
            'name' => 'Identical',
            'options' => array(
                'token' => '3',
            ),
        ),
    ),
));

$form->setInputFilter($inputFilter);
...

This would not work because on validation the validator would try to find '3' in the context, and then rise an exception when it doesn't find it.

To solve this I add a new option, literal. Setting this to true (it's false by default) would allow a 'literal' validation even when the context is provided. So the above input filter would look like this:

$inputFilter->add(array(
    'name' => 'humanCheck',
    'required' => true,
    'validators' => array(
        array(
            'name' => 'Identical',
            'options' => array(
                'literal' => true,
                'token' => '3',
            ),
        ),
    ),
));

This would tell the validator to skip the look up in the context and just use the string '3'.
_Note: this option has no affect when context is not provided._

[blanchonvincent]

why you add a space ?

[iquabius]

To align with the line below!

[iquabius]

@bakura10 sent this PR (#3869), to fix a BC break originated from this PR (#3803). If his PR is really necessary, this one isn't.

I think this new option is a good idea, if it can't be in this version, it could be added in some next version (from what I see just in ZF 3.0, right!?)

So someone take a good look and decide what is the best solution!

[bakura10]

I think we need to merge my PR, yours still introduce a BC that is not necessary. As you said, you need to keep this for ZF 3 :).

[Freeaqingme]

As per the comments, I'll assign this issue to version 3.0.0, that will give us plenty of time to think about it and review it ;)

Nonetheless I'd like to thank you for your PR, we have plenty of other issues that you may be willing to work on in the meanwhile! =)

[weierophinney]

I think I'm missing something; I don't see anything backwards incompatible in this PR. I think we can merge this for 2.2.0.

[iquabius]

The BC break was fixed with @bakura10's PR. When I first introduced the ability to validate in fieldsets, the line 174 was throwing an exeption - that happened in the case a $context was provided and the given token didn't existed. Now the behavior is to use the token literally if this happens - the bad thing about this is that if you type a wrong token, you will never know why your fields are not validating, but this was necessary to remove the BC break.

I actually didn't realize this PR could still be used.

[weierophinney]

Forgot to close when I merged!