Hide all admin menu items from non admin users. Refs T682

Summary: Hide all admin menu items from non admin users

Test Plan:
Log in as a normal user: check you cannot see settings/manage links in the menu
Log in as an admin: check you can see settings/manage links in the menu

Reviewers: aMoniker, shadowhand

Reviewed By: aMoniker, shadowhand

Maniphest Tasks: T682

Differential Revision: https://phabricator.ushahidi.com/D355