Start on a /force_auth screen.

Work to be done:
* Forgot password screen needs its links to now allow signup/signin, just back.
* Would be nice to combine code with /signin view somehow.
If user accesses reset_password from the force_auth screen, only show a back link.

* Save forceAuth to the session. If forceAuth is set, only show back button in the reset_password screen.
* Reset the forceAuth flag from sign_in and sign_up