Fix issues with the borders/corners around datagrids.

On the datagrids (all but the dashboard), the title header didn't have
rounded corners, making the background stick out just a bit.

On the bottom of the datagrid, the last item did the same thing. The
last entry now should always have rounded corners.

There was a small issue with the padding at the bottom of the box for
datagrids that made the rounding at the bottom look wrong. This was 1px
padding that IE needed. We now target IE specifically for that padding
with a little hack.
Add support for registered GitHub OAuth applications.

Registered GitHub OAuth applications have the added benefits of central
revocation of a key and higher rate limits. While it's not possible for
us to turn this on for every installation out there (since sharing a
client secret is a very bad idea), those who need it can register their
own application entry and set it up with Review Board.

This is a pretty advanced feature, so there's no UI-side configuration
for this. Those who need it are expected to set the
settings.GITHUB_CLIENT_ID and GITHUB_CLIENT_SECRET keys.
Merge branch 'release-1.7.x'