With a recent change in i18n, default language is not
included in fallbacks by default. This causes that
MissingTranslationData exception is raised both in
development and production mode.

This patch sets explicitly fallbacks language to english
which assures that english is used for missing translations.

Adds support for https://gitlab.com/gitlab-com/infrastructure/issues/57

`config.assets.compress` needed to be explicitly enabled.

Follow-up to !3544. Resolves #14344.

> The config.assets.compress option should be changed to config.assets.js_compressor like so for instance

Also add support for connecting to Redis with Unix sockets.

Before this change, Rails cache data was stored in a global Redis
namespace. As a consequence, clearing the Rails cache (`rake
cache:clear`) would also delete all Sidekiq queue data and session
storage. This change puts all Rails cache data in a `cache:gitlab`
namespace, making `rake cache:clear` safe again.

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

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

  * Remove trailing whitespace
  * Converts hard-tabs into two-space soft-tabs
  * Remove consecutive blank lines