refactor(client): Move many parameters/helpers from Session/ServiceMixin to the Reliers.

parameters:

* service
* most oauth parameters
* redirectTo
* context

helper functions:

* isSync
* isFxDesktop

Other work:

* Split of the OAuthRelier from the normal Relier
* Initialize Channels with the Relier in app-start
* Update the oauth-reset-password functional test to not hard code the email format. Instead fetch the link from the email headers.

Remove all of the resume stuff.

issue #1648
feat(client): Seemless verification in a second browser.

* Create a `resume` token from OAuth parameters. Pass it along to the fxa-js-client.
* Re-populate OAuth parameters from resume token on email verification.
* Bump fxa-js-client to 0.1.25 with the new `resume` hotness.
* Add functional tests for verifying in a second browser.
* Only show the serviceName in the ready screen if the user can continue with the OAuth flow.

issue #1623