We now handle authentication requests via an `about:` page
which presents a nice form built into the browser window.
In order to do this, we add internal navigation as a concept
to the browser window and we strip the 401login support from all
frontends except monkey.
The 401login callback is now intended for password safe type support
rather than an immediately interactive prompt.
Signed-off-by: Daniel Silverstone <dsilvers@digital-scurf.org>
