GitLab uses the import_project method in GitLab Shell,
This method uses a timeout for the operation, hardcoded to 800 seconds.
With this MR the timeout is now configurable in the gitlab_shell
settings.

Hard-coding location of configuration files is very bad practice. This
patch applies the same approach as currently used for
gitlab_shell_secret file.

Closes gitaly#166

Use full path for moving directories when changing namespace path

See merge request !2078

Note that the old migrations depend on 1_settings.rb, so we can't
quite remove those completely.

If there is an existing gitlab.yml file with snippets explicitly
disabled, they won't be enabled with this change.

This will be necessary when adding gitaly settings. This version
doesn't make any functional changes, but allows us to include this
breaking change in 9.0 and add the needed extra settings in the future
with backwards compatibility

- The pages are created when build artifacts for `pages` job are uploaded
- Pages serve the content under: http://group.pages.domain.com/project
- Pages can be used to serve the group page, special project named as host: group.pages.domain.com
- User can provide own 403 and 404 error pages by creating 403.html and 404.html in group page project
- Pages can be explicitly removed from the project by clicking Remove Pages in Project Settings
- The size of pages is limited by Application Setting: max pages size, which limits the maximum size of unpacked archive (default: 100MB)
- The public/ is extracted from artifacts and content is served as static pages
- Pages asynchronous worker use `dd` to limit the unpacked tar size
- Pages needs to be explicitly enabled and domain needs to be specified in gitlab.yml
- Pages are part of backups
- Pages notify the deployment status using Commit Status API
- Pages use a new sidekiq queue: pages
- Pages use a separate nginx config which needs to be explicitly added

Code improvements, bug fixes, finish documentation and specs

[ci skip]