Merge branch 'super-secret-login-upgrade' into 'master'

Revert signin tab order fix.

The history: 

> 1. @sytses created this: https://gitlab.com/gitlab-org/gitlab-ce/issues/23279
> 2. The fix was submitted here: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6867
> 3. I [made](https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6867#note_16993324) the same observation you did after it was merged
4. A long discussion about accessibility and UX followed, and we decided to revert all changes (https://gitlab.com/gitlab-org/gitlab-ce/issues/23698).

## Screenshots (if relevant)

![2016-11-17_20.55.22](/uploads/c81b0bbe0cd08747124531778af6273f/2016-11-17_20.55.22.gif)

## Does this MR meet the acceptance criteria?

- [x] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) added
- [x] All builds are passing
- [x] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/23698

See merge request !7538

app/assets/stylesheets/pages/login.scss

@@ -255,26 +255,3 @@
   }
 }
 
-// For sign in pane only, to improve tab order, the following removes the submit button from
-// normal document flow and pins it to the bottom of the form. For context, see !6867 & !6928
-
-.login-box {
-  .new_user {
-    position: relative;
-    padding-bottom: 35px;
-
-    @media (min-width: $screen-sm-min) and (max-width: $screen-sm-max) {
-      .forgot-password {
-        float: none !important;
-        margin-top: 5px;
-      }
-    }
-  }
-
-  .move-submit-down {
-    position: absolute;
-    width: 100%;
-    bottom: 0;
-  }
-}
-

app/views/devise/sessions/_new_base.html.haml

@@ -5,8 +5,6 @@
   %div.form-group
     = f.label :password
     = f.password_field :password, class: "form-control bottom", required: true, title: "This field is required."
-  %div.submit-container.move-submit-down
-    = f.submit "Sign in", class: "btn btn-save"
   - if devise_mapping.rememberable?
     .remember-me.checkbox
       %label{for: "user_remember_me"}
@@ -14,3 +12,5 @@
         %span Remember me
       .pull-right.forgot-password
         = link_to "Forgot your password?", new_password_path(resource_name)
+  %div.submit-container.move-submit-down
+    = f.submit "Sign in", class: "btn btn-save"