Add ability to toggle each panel from the frontend

[jezdez]

I was wondering if it would be a good idea to provide a separate panel that would allow the user to toggle each panel from the frontend. That'd useful e.g. in case the SQL panel takes to long to render and wouldn't require deactivating it site-wide.

Additionally this could be only used on a specific url/path, so that the toggle would survive clicking around the site. That option would be given the user to make in the panel, too.

I guess the toggle state could be saved in a cookie.

[robhudson]

Agreed, this would be a good addition. The user interface for such a thing might be difficult. There have been times, with large Django installations, that I've had to disable most panels to get a reasonable time to render the response (due to the (a) extra introspection the debug toolbar has to do, (b) the extra template rendering, and (c) the extra HTML rendering by the browser).

I think saving state is best done in the cookie, similar to how we're saving the minimized state there already.

[aaugustin]

@jezdez @robhudson Could you try this pull request?

I find it slightly unintuitive that toggling checkboxes has no effect until the next request. But it gets the job done...