Add options to disable the collapse, add-property and remove-property buttons.

I'd like to use this for end-users to render a normal HTML form, but the various in-built form editing tools are inappropriate for this use case. So I've added options to disable them:

        no_additional_properties: true,
        disable_edit_json: true,
        disable_collapse: true,
        disable_remove_links: true

![image](https://cloud.githubusercontent.com/assets/1751645/2741252/3bb6988a-c6e4-11e3-9302-bbff739d76fa.png)