Fix to make sure the js bridge code is only enabled when qute: pages are shown.
Previously it would only be available to the first page (and before that it
was available to all pages).
Add the ability to view/edit the browser's config settings via a special
browser page.
It's very simplistic for now, but a good starting point.
Future possibilities:
* Matching config types to html input types
* colors = html colorpicker
* options with valid_values = select/multi-select
* plain text fallbacks where appropriate
* multi-line text edits for long options (i.e. host-block-lists)
* Javascript option verification
* switch from submitting changes onblur to onchange if an option passes basic
verification, etc.
