Merge pull request #406 from 18F/feature/2fa

Feature/2fa
factor out roles helper into module

Becuase `Doorkeeper::ApplicationController` does not inherit from our `ApplicationController`, it does not get helper methods defined in `ApplicationController` ... but it can get mixins.
Merge pull request #415 from 18F/hotfix/roles_helper

factor out roles helper into module
Add tests around session controller redirects

Test that the redirects are working correctly for various states of signed-in-ness.
Merge pull request #416 from 18F/hotfix/session_controller_redirect_specs

Add tests around session controller redirects
Fix the MyUSA URL sent out in mails
Merge pull request #418 from 18F/hotfix/staging-mail-url

Fix the MyUSA URL sent out in mails
Update legal documentation
Add auto-generated files from rake task
Merge pull request #420 from 18F/hotfix/pra

Update legal documentation
Merge branch 'devel' into feature/error_pages
Treat 401/unauthorized as 404