Fix PEP-257 issues in reviewboard/datagrids

Review Request #7249 — Created April 24, 2015 and submitted — Latest diff uploaded

Information

Review Board
release-2.5.x
5ae50b0...

Reviewers

This cleans up existing docstrings and adds missing ones in the
reviewboard/datagrids directory.

Ran pep257 --ignore=D100,D203 reviewboard/datagrids.