Feaure ldap oauth tests

Concerns #154 Improve LDAP test coverage

See merge request !167

Pull external issue tracker fix from ce

See merge request !171

Update markdown reference to external issues
Conflicts:
	lib/gitlab/markdown.rb

Rename enterprise linux to centos

/cc @jacobvosmaer

See merge request !166

Appearances to appearance

See merge request !170

Issue imporve ldap group link error msg

I've improved the flash message with the exact error.

See merge request !168

Should prevent CI failure

Feature 120 multiple ldap groups

Fixes issue found in QA tests

- #158 inconsistent success behaviour for admin#ldap
- #157 Wrong navigation bar in group/ldapgrouplinks

See merge request !164

This will prevent a mess, and keeps everything clean.
In addition i made the non interface methods private

Same patch as gitlab-ce
https://dev.gitlab.org/gitlab/gitlabhq/merge_requests/1053

Documentation for multiple LDAP group links

See merge request !165

Improve explanation of the LDAP permission reset

See merge request !163

Fixes #157

Add support for multiple LDAP groups per Gitlab group

concerns #120

See merge request !143

Conflicts:
	app/models/group.rb
	app/views/groups/members.html.haml
	db/schema.rb

Packages for 7.2.1-ee

See merge request !162

Add 7.2.0-ee packages for Centos 7

See merge request !161