Issue 2034 redirect flow

@seanmonstar - I have taken your initial code and made it work initially for Chrome for iOS and Windows Phone 7.5+.

An ephemeral instance is set up to play with.

There is an issue with the cert on personatest.org, in Windows Phone, the user has to first visit redirect-flow.personatest.org to accept the cert, then redirect-flow.personatest.org.

I have added two new options to the navigator.id.request API, these are up for debate, but it is a way to test.

* allowRedirect - allows redirect if we detect a device does not support popups. I preffed this on instead of just allowing it so that RPs do not unwittingly lose JS state upon redirect. They have to opt in to allowing redirect.
* forceRedirect - force the redirect flow.