Add "almanac.namespace.edit" and "almanac.namespace.search" API methods

Summary: Depends on D19336. Ref T13120. Ref T12414. These are simple, straightforward, and uninteresting.

Test Plan:

• Searched for namespaces with "almanac.namespace.search".
• Created and edited namespaces with "almanac.namespace.edit".

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13120, T12414

Differential Revision: https://secure.phabricator.com/D19337