Boolean values for use with checkbox/radio buttons/etc

[leightonthomas]

Any non-text field doesn't re-populate though the data will get saved.
For example,

$builder
    ->add(
        'my_setting',
        'checkbox',
        [
            'required' => false
        ]
    )
    ->add('Save', 'submit', ['attr' => ['class' => 'btn btn-flat btn-primary']]);

would save a checked box as 1 which is what we want, but upon loading the page again the box will be unchecked. I think this is because it isn't converted to the correct type depending on what the form is expecting (e.g. a boolean for a checkbox)