Add minimum requirements for Elasticsearch



See merge request !130

[ci skip]

Elastic search improvements

* Remove warning when you run index_repositories task first time and there is no index yet.

* Update wiki index dynamically. It has been forgotten.


See merge request !126

Update changelog



See merge request !128

Elasticsearch integration

https://gitlab.com/gitlab-org/gitlab-ee/issues/61

Steps:

- [x] Base integration
- [x] Implement snippet search (service lawyer and actual search)
- [x] Implement project search (service lawyer and actual search)
- [x] Implement global search (service lawyer and actual search)
- [x] Implement search through the notes
- [x] Implement search through the milestones
- [x] Implement search though the wiki blobes
- [x] Implement search though the commits and code
- [x] Specs and Spinach (fix)
- [ ] Specs and Spinach (new ones)
- [x] Take care of omnibus support for elasticsearch 
- [x] Documentation
- [ ] Add elasticsearch check to GitLab check
- [x] Update and create index means

See merge request !109

Hide issues settings when issues are disabled

This closes gitlab-org/gitlab-ee#198

/cc @DouweM @axil @JobV 

See merge request !122

[ci skip]

[ ci skip]

See merge request !115

Fix alignment issues after a fix on titles weight

Fixes #8102. Fixes #3956. This fixes an alignment regression introduced by !2422. Sorry about that! :/

## Commit title alignment fixed

![Screen_Shot_2016-01-14_at_16.10.01](/uploads/8fdc08dca379bc551f5872de910c7149/Screen_Shot_2016-01-14_at_16.10.01.png)

**The fact that the first row has a smaller height than the other rows was not introduced by !2422 (I've checked by reverting 818607f0 on `master`).**

## Tags name in list

![Screen_Shot_2016-01-14_at_16.10.09](/uploads/fba3978037677bb8855f374b5f38dde0/Screen_Shot_2016-01-14_at_16.10.09.png)

See merge request !2431