Classifier render 'type' property

[brownhoward]

User Story

As a Form Designer, I can specify a Classifier render type, so I can provide the renderer guidance on how a Classifier field should be rendered (e.g., list, dropdown, radio buttons, etc.).

Acceptance Criteria

1. In the Form Model, the type of control to use to render a Classifier can optionally be defined using a 'type' property. Possible values include 'list', 'dropdown', 'radiobuttons'.
2. When the form is rendered based on the Form Model, if possible the Classifier is rendered using the suggested type of control. If the 'type' is not specified, a dropdown should be used.