Update imports for the new Djblets file restructure.

Review Request #4951 — Created Nov. 13, 2013 and submitted

Information

Review Board
master

Reviewers

Update imports for the new Djblets file restructure.

djblets.util is largely being split up, and while the old imports still
work, they emit deprecation warnings. This change updates Review Board
to use the new locations of the classes and functions it was previously
accessing from djblets.util.

Unit tests pass.

Site seems to work.