devise: unify password reset views

By default, Devise will look for views:

1. First in `views/resource/passwords/…`,
2. Then in `views/devise/passwords/…` if not found.

By moving the views to `views/devise`, we avoid having a partial in
`views/shared` that we need to include manually, and instead let Devise
do the job automatically.

app/views/devise/passwords/edit.html.haml

@@ -0,0 +1,22 @@
+- content_for(:title, 'Changement de mot de passe')
+
+- content_for :footer do
+  = render partial: 'root/footer'
+
+.container.devise-container
+  .one-column-centered
+    = devise_error_messages!
+
+    = form_for(resource, as: resource_name, url: password_path(resource_name), html: { method: :patch, class: 'form' }) do |f|
+
+      %h1 Changement de mot de passe
+
+      = f.hidden_field :reset_password_token
+
+      = f.label 'Nouveau mot de passe'
+      = render 'password_complexity/field', { form: f, test_complexity: populated_resource.validate_password_complexity? }
+
+      = f.label 'Confirmez le nouveau mot de passe'
+      = f.password_field :password_confirmation, autocomplete: 'off'
+
+      = f.submit 'Changer le mot de passe', class: 'button large primary expand', id: "submit-password", data: { disable_with: "Envoi…" }