Make Portals indexable with Ferret

Summary:
Ref T13275. Add portals to the search index so that:

• they show up in fulltext global search; and
• the typeahead actually uses an index.

Also make them taggable with projects as an organizational aid.

Test Plan: Indexed portals with bin/serach index, searched for a portal with "Query", with fulltext search in main menu, with typehead on "Install Dashboard...", changed the name of a portal and searched again to check that the index updates properly.

Reviewers: amckinley

Reviewed By: amckinley

Subscribers: PHID-OPKG-gm6ozazyms6q6i22gyam

Maniphest Tasks: T13275

Differential Revision: https://secure.phabricator.com/D20389