Add a paginated list of all repository tags to Diffusion

Summary: Now supports more than 25 tags!

Test Plan: Set page size to 1, paginated. Verified SVN / Hg don't break/explode.

Reviewers: davidreuss, vrana, btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T1130

Differential Revision: https://secure.phabricator.com/D2268