Change Ponder default query to 'Recent'

Summary: In Ponder, I think the right default query is "good" questions. That being recently asked, and either open or resolved. For browsing this seems correct. For moderators, I presume they use saved queries accordingly. This is similar to stack overflow and quora.

Test Plan: Review queries in my dev box, all seems to run correctly

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D13877