Add a `addColumns` method to `PhutilConsoleTable`.

Summary: Allow columns to be added in one big hit. In some cases, this may be easier than adding columns individually.

Test Plan: Meh

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9553