Removing responsibility of Form class to know about FormRows.

Instead, just grab the row with getRow().
Trimming more methods from Form.
Fixing CsrfListener to use the Row.
Adding option to ignore unknown rows in setValues.
Adding option to ignore unknown rows in setErrors().
Removing Form::addRule().
Adding Html::addToAttribute().
Adding Html::addToAttributeArray().
Html::addToAttribute() can now handle abitrary whitespace.
Creating RendererInterface to remove Html from row classes.
Row classes now deletage Html rendering to renderers.

Rendering errors and labels is now the responsibility of a renderer.
Text now uses renderers.
Textarea row now uses renderers.
Password now delegates html rendering.
Hidden now implements required interface.
Checkbox now uses RendererInterface.
Testing Html::select() with strange types.
Updating Select row to work with renderers.
Submit row now uses RendererInterface.
Updating Form to use a default renderer.