Implements Spaces application in Slowvote

Summary: Implements T8733

Test Plan: Verify that spaces policies can be implemented in the creation and editing of polls.

Reviewers: lpriestley, epriestley, Blessed Reviewers

Reviewed By: epriestley, Blessed Reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D13537