Update links in help menu

The left-bottom Help menu in the CMS has these hardcoded links:

• http://support.bloomreach.com
• https://documentation.bloomreach.com/library/end-user-manual/end-user-manual-introduction.html
• https://help.bloomreach.com/

1) Since the merge of SM and XM documentation, the 3rd link redirects to the 2nd, so we can change this.

2) 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.

(Created CMS-14242 for this)