Move slowvote loading logic into Query class

Summary: Mostly straightforward. Also fixed a couple of error/darkconsole things.

Test Plan:

• Created poll;
• viewed poll;
• voted in poll;
• used V6 and {V6} markup styles in poll.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Differential Revision: https://secure.phabricator.com/D6458