Add back-up account step to "forgot password" flow

[anikarni]

The "add back-up account" page is already implemented, but we should make sure that users that come into the flow through "forget password" should also be able to setup a back-up account and have the new recovery code sent to them again.

Design Some things have changed, but basic idea is Mobile: https://projects.invisionapp.com/share/YXB1ZMJBG#/screens/226009156 (last step) Desktop: https://cloud.githubusercontent.com/assets/7905650/24221915/f103873a-0f2e-11e7-807c-61e1c496882d.png

Acceptance Criteria

When I submit my recovery code, I should see the "back-up account" step.

In Scope

• Add back-up account page to "forgot password" flow
• Make sure the validation and error treatment is used here

Out of Scope

• Design -- the page should aready be created

Depends on

932 , #922