Remove Session.isOAuth & Session.isFxDesktop, this info now resides on the Relier.

* Update all locations that query Session for this information.
* Initialize Channels with the Relier in app-start
No longer save "client_id" to Session, this is taken care of by the relier.
Always sign in after a password reset so that assertions can be generated and sent to the OAuth RP.
Update the oauth-reset-password functional test to not hard code the email format. Instead fetch the link from the email headers.