Configuration example for issue tracking in Trac. And added :project_name placeholder in URLs for tickets.

Example for multiple trac instances hosted on the same host.
Multiple gitlab repositories can map into a single trac instance using keywords field in tickets.
Adding support for customized avatar services.

This new feature allows the user avatars to be fetched from any other service, based on any of the users details, such as the username.
The lookup is performed by email, to load the user record, and then a given field is extracted from the user record to be substituted on the avatar image URL format string.

Conflicts:
	app/helpers/application_helper.rb
	config/gitlab.yml.example
Shibboleth integration and omniauth/LDAP code clean up.

Configuration format now handles arbitrary omniauth modules.
LDAP is treated just like Shibboleth and any other omniauth authentication method.
With Shibboleth, the login screen in Gitlab is hidden and session is started automatically because the user can only access the site after successful login on Single Sign On.
These changes require gem omniauth-shibboleth 1.0.7 or later.
Hide social accounts configuration and password change form.

This makes sence on a corporate setup where SSO is enforced, and
therefore social accounts won't be used for authentication.
Plus, at least when using Shibboleth, it makes no sence to show the
password change form in Gitlab.
Hide HTTP repository clone URL.

When the application is behind Shibboleth access control,
the HTTP Basic Auth will not work and therefore HTTP access to
repositories is not possible.
Hide HTTP wiki repository clone URL.

The same that was done for main repository HTTP clone URL.
Merge remote-tracking branch 'origin/5-4-stable-sso' into 5-4-stable-sapo
Merge remote-tracking branch 'origin/5-4-stable-trac' into 5-4-stable-sapo
Merge remote-tracking branch 'origin/5-4-stable-avatar' into 5-4-stable-sapo