Make Portals reachable without knowing the URI

Summary:
Depends on D20360. Ref T13275. This makes the "Dashboards" application start on a Drydock-like console page where you pick portals, dashboards, or panels.

Probably the "Dashboards" application should either be renamed to "IntelliknowledgePro" or Portals should be split off into a separate application eventually, but let's see how things go like this for now, since restructuring probably breaks some URIs at least a little bit so I'd like more confidence that we're headed in the right direction before we do it.

Test Plan:

• Visited Dashboards via typeahead, got options for Dashboards/Portals/Panels.
• Visited Portals pages, got simplified crumbs.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13275

Differential Revision: https://secure.phabricator.com/D20361