Do some initial y2020 drivetrain tuning

1) Makes the drivetrain replay work in a multinode world.
2) Tweaks localizer and spline constants.
3) Initializes the localizer at the start of auto.
4) Runs a simple s-spline in auto, just for kicks.

Change-Id: I1cf990ee8d0c0811fa1e8de7b62209eb0260fa29
diff --git a/frc971/control_loops/drivetrain/hybrid_ekf.h b/frc971/control_loops/drivetrain/hybrid_ekf.h
index d2c0be3..cb50165 100644
--- a/frc971/control_loops/drivetrain/hybrid_ekf.h
+++ b/frc971/control_loops/drivetrain/hybrid_ekf.h
@@ -146,7 +146,7 @@
   static constexpr int kNOutputs = 3;
   // Time constant to use for estimating how the longitudinal/lateral velocity
   // offsets decay, in seconds.
-  static constexpr double kVelocityOffsetTimeConstant = 10.0;
+  static constexpr double kVelocityOffsetTimeConstant = 1.0;
   static constexpr double kLateralVelocityTimeConstant = 1.0;
   // Inputs are [left_volts, right_volts]
   typedef Eigen::Matrix<Scalar, kNInputs, 1> Input;
diff --git a/frc971/control_loops/drivetrain/splinedrivetrain.h b/frc971/control_loops/drivetrain/splinedrivetrain.h
index b28334c..051e71a 100644
--- a/frc971/control_loops/drivetrain/splinedrivetrain.h
+++ b/frc971/control_loops/drivetrain/splinedrivetrain.h
@@ -138,7 +138,7 @@
       (::Eigen::DiagonalMatrix<double, 5>().diagonal()
            << 1.0 / ::std::pow(0.12, 2),
        1.0 / ::std::pow(0.12, 2), 1.0 / ::std::pow(0.1, 2),
-       1.0 / ::std::pow(1.5, 2), 1.0 / ::std::pow(1.5, 2))
+       1.0 / ::std::pow(1.0, 2), 1.0 / ::std::pow(1.0, 2))
           .finished()
           .asDiagonal();
   const ::Eigen::DiagonalMatrix<double, 2> R =