Add all Geo docs to navigation

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/13443.

Completes categorizing and adding Geo documentation to the global nav.

• Replication:
  • Before: https://docs.gitlab.com/ee/administration/geo/replication/index.html
  • After: http://add-all-geo-docs-to-nav.178.62.207.141.xip.io/ee/administration/geo/replication/
• Disaster Recovery:
  • Before: https://docs.gitlab.com/ee/administration/geo/disaster_recovery/index.html
  • After: http://add-all-geo-docs-to-nav.178.62.207.141.xip.io/ee/administration/geo/disaster_recovery/

These are menu-only changes, and allow all the Geo docs to-date to be navigable by the Global Nav.

We couldn't support ( or ) in the navigation, so I had to add support for that.

CC @mkozono @ashmckenzie