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/y2020/control_loops/drivetrain/drivetrain_replay.cc b/y2020/control_loops/drivetrain/drivetrain_replay.cc
index af6a841..faf2cef 100644
--- a/y2020/control_loops/drivetrain/drivetrain_replay.cc
+++ b/y2020/control_loops/drivetrain/drivetrain_replay.cc
@@ -41,15 +41,19 @@
                             "frc971.control_loops.drivetrain.Output");
   reader.Register();
 
+  const aos::Node *node = nullptr;
+  if (aos::configuration::MultiNode(reader.configuration())) {
+    node = aos::configuration::GetNode(reader.configuration(), "roborio");
+  }
+
   aos::logger::DetachedBufferWriter file_writer(FLAGS_output_file);
   std::unique_ptr<aos::EventLoop> log_writer_event_loop =
-      reader.event_loop_factory()->MakeEventLoop("log_writer");
+      reader.event_loop_factory()->MakeEventLoop("log_writer", node);
   log_writer_event_loop->SkipTimingReport();
-  CHECK(nullptr == log_writer_event_loop->node());
   aos::logger::Logger writer(&file_writer, log_writer_event_loop.get());
 
   std::unique_ptr<aos::EventLoop> drivetrain_event_loop =
-      reader.event_loop_factory()->MakeEventLoop("drivetrain");
+      reader.event_loop_factory()->MakeEventLoop("drivetrain", node);
   drivetrain_event_loop->SkipTimingReport();
 
   y2020::control_loops::drivetrain::Localizer localizer(