Remove access control for uploaded images to fix broken images in emails

Replaces !530.

> This MR removes the access control for uploaded images. This is needed to display the images in emails again.
>
> The previous solution to base64 encode the images had to be reverted, because not all email clients supported it.
>
> If possible this should go into the 7.10 release.

See merge request !533

Ignore submodules that are defined in .gitmodules but are checked in as directories.

Pulls in gitlab_git 7.1.10 which contains gitlab-org/gitlab_git!26.

Fixes #1439 and https://github.com/gitlabhq/gitlabhq/issues/9140

See merge request !540

Fixed typo in deploy html

do not prepend relative_url_root to avatar

Parse GFM references after sanitizing

Parse GFM references - labels, issues, MRs, etc. - after calling the HTML Pipeline `SanitizationFilter` so that we can use non-whitelisted attributes like `style`.  See #2188.

See merge request !1745

Fix label color input.

Because `value` was set, every label color would render as purple in the form.

Introduced by 83b5a9ae2bfb594bcb5a9a931d6781ba05c9b9ef between 7.9 and 7.10, so no changelog item.

See merge request !538