(Backport 15) Make links configurable in help menu / hide help menu

Story:

As a system admin I would like to configure the menus in the help menu to suit my own environments

Acceptance criteria:

1) The name and URL of a help menu link can be changed by customers per environment

2) The default configuration if no menus are defined should be as described in ENT-5013

! Backport to the next PaaS release

Description:

The left-bottom Help menu in the CMS 

Since not all editors have access to the portal (1st link), clients may want to change the menu. A good option would be to make the links configurable.

Otherwise, have the possibility to not show the help menu at all.