Tune localizer, remove error states

Tuning constants are from whatever I was running yesterday.

More substantially, I removed the voltage error and angular error states
(during the day I had just zeroed them out on every iteration, but
actually removing them reduces the dimensionality of the EKF, which is
nice). When I looked at the log streamer when we were running the robot,
it just looked like the voltage error terms were oscillating a bit
around zero, suggesting that they were just being counterproductive.

Change-Id: I9744c4808edf3a43ae1c76d022460ee1d4c9ed3e
diff --git a/frc971/control_loops/drivetrain/BUILD b/frc971/control_loops/drivetrain/BUILD
index a4d2ca6..d3ed728 100644
--- a/frc971/control_loops/drivetrain/BUILD
+++ b/frc971/control_loops/drivetrain/BUILD
@@ -46,6 +46,7 @@
     deps = [
         ":drivetrain_config",
         "//aos/containers:priority_queue",
+        "//aos/util:math",
         "//frc971/control_loops:c2d",
         "//frc971/control_loops:runge_kutta",
         "//third_party/eigen",