Partially addresses #47424.

Fixes project visibility guidelines

See merge request gitlab/gitlabhq!2226

(cherry picked from commit 877c42c0aaf3298d6001614c9706bc366ae4014c)

e4fd1c26 Ensure project wiki visibility guidelines are met

This reverts merge request !14148

Revert "Merge branch '35012-navigation-add-option-to-change-navigation-color-palette' into 'master'"

This reverts merge request !13619

Fixes gitlab-org/gitlab-ce#17489

Fix test finding two of the same element

Capybara will raise an exception because it finds two elements that
match .nav-links. This means this test would fail, even if the page
meets the conditions for passing the test.

Add more tests for guest access

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

adds fix for security issue when annonymous user does not have access to repository we now display the activity feed instead of the readme

Fixes #14585.

Closes #2662

Update PreferencesHelper specs

Instead of rendering this value server-side, we use Javascript and Gon
to apply the user's color scheme (or the default) to any syntax
highlighted code blocks.

This will make it easier to cache these blocks in the future because
they're no longer state-dependent.

Very similar to Gitlab::Theme, this contains all of the definitions for
our syntax highlighting schemes.

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Consolidates the helpers related to user preferences.

Renames `app_theme` to `user_application_theme` to better explain what
it is.