Indicate what flavour of GitLab you're using: CE or EE

Description

Sometimes GitLab users do not even know are they on CE or on EE. It would be good to add an interface element with will indicate it.

Original suggestion

Design

Add a link to the bottom of the global menu. The link should say About GitLab CE or About GitLab EE depending on version. Clicking this link should take you to /help.

cc @JobV