Allow Almanac namespaces to be searched by ngram index

Summary: Ref T6741. Ref T10246. This is largely modernization, but will partially support namespace locking in Almanac.

Test Plan:
Searched for Almanac networks by name substring.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T6741, T10246

Differential Revision: https://secure.phabricator.com/D15322