Recover password form, mailer.

[rpales]

• Added prepend: true to protect_from_forgery as this is not executed before callbacks in rails 5 and causes issues (https://github.com/rails/rails/commit/39794037817703575c35a75f1961b01b83791191).

• Added "empty" PasswordsController to override default's Devise::PasswordsController if needed.

• Edit view templates views/devise/passwords/new and views/devise/passwords/edit for "send recovery link" form and "change password" form, respectively.

• Edit views/devise/mailer/reset_password_instrucctions.html.erbas needed.

Note: In regards with uploads (such as user avatars), if you were to load balance a multi-host deployment, these should be stored either using a shared NFS mounted folder or S3 using Fog. We can setup the latter for you if you pass us AWS S3 credentials.