Clean up overlap between dashboard and explore

• Clean up overlap between dashboard and explore. ... 5d785457
  • Split up SnippetsController into separate dashboard and explore sections.
  • Use consistent page titles, header titles and sidebars between dashboard and explore sections when signed in or not.
• Consistently case Back to X links. 260fcd45
• Link to help from signin page bottom. d92696d3
• Make Help accessible for guests. c258e977

cc @dzaporozhets