WIP: gitlab: Upgrade to 8.8.9 + start automation of gitlab-backup

Upgrade

* GitLab Software + patches ported to GitLab 8.8.9;
* Configs synced with upstream and SlapOS-ified;
* Fix promises due to curl upgrade

@jerome @kazuhiko @kirr: if you have any comments, I would be glad to read them. There is a demo instance you can try.

Check on the demo instance for the Gitlab configuration:

• migrations are all up, when running: gitlab-rake db:migrate:status
• promises don't fail (including slow ones)
• web UI seems fine
• git clone/fetch/push works well
• email notifications are sent

and Nexedi edition patches:

• raw blobs download
• private ones with gitlab-ci token curl -v https://user:token@testinstance/kirr/test/raw/master/hello.txt
• applying patches in merge-request
• merge as topic in merge-request
• "Nexedi edition" being present on front page and on page footers with ICP
• clone protocol is only HTTPS (not SSH)

No changes are made in gitlab-workhorse and gitlab-shell upstream this time, but Nexedi patches and a cherry-picked commit are applied in a merge request on gitlab-ce.

Note: in order to build the gitlab SR, you need to change gitlab-ce repository to my own, as it is not merged yet:

--- a/software/gitlab/software.cfg
+++ b/software/gitlab/software.cfg
@@ -115,7 +115,7 @@ git-executable = ${git:location}/bin/git
 [gitlab-repository]                                                                            
 <= git-repository                                                                              
 #repository = https://gitlab.com/gitlab-org/gitlab-ce.git                                      
-repository = https://lab.nexedi.com/nexedi/gitlab-ce.git
+repository = https://lab.nexedi.com/iv/gitlab-ce.git

Gitlab backup (pull automation)

The idea is to regularly do a gitlab-backup pull for now, so that later, we can add some code to configure the other gitlab instance (not in production) to pull the created backup repo.