Html data attributes are automatically encoded as JSON
Revert "buttons and hidden fields are generated without HTML attribute ID. By default. (BC BREAK!)"

This reverts commit 1937a29f3200b6be9f6c7aed695eeafc75827a5d.
Revert "Forms: all validators and $defaultMessages moved to new class Nette\Forms\Validator (BC break if you are calling these methods directly)"
Revert "DefaultFormRenderer already does not modify the HTML class of controls. Classes are applied only when form is rendered. (BC break)"

This reverts commit bbc47eeef14389d71a42ffe5949120d677745d5a.
Revert: Forms: $cols & $rows do not trigger error