Update the documentation for the LDAP user filter
Keep the legacy LDAP syntax in the documentation
Remove legacy LDAP configuration examples
Add LDAP configuration documentation
Merge request for blog post on gitlab.com next time.
Merge branch 'master' of dev.gitlab.org:gitlab/gitlabhq
Merge branch 'doc-ldap_user_filter' into 'master'

Update LDAP documentation

See merge request !1199
Merge branch 'master' of dev.gitlab.org:gitlab/gitlabhq