Config form styling is pretty hard to override at times, since it's so

deeply nested and contains styling for most elements one would want to

override.
This change flattens that styling, making it much easier to override in

other stylesheets. There's still some cleanup that could be done

(reordering of rules to match conventions, and moving some rules

specific to Review Board out), but that can be done in a follow-up

change.

Went through all the pages we have in Review Board and RBCommons that

make use of configforms styling. Verified everything looked correct

and matched other instances.