Pre-plan auto splines

(a) Make it so that the drivetrain automatically evicts old splines
(b) Set up auto to preplan splines at construction and after every auto.

Change-Id: I96ddb3a38947da02ad9ddc6fe933b7e85727dc18
diff --git a/frc971/autonomous/BUILD b/frc971/autonomous/BUILD
index c9eb49e..c7f2d20 100644
--- a/frc971/autonomous/BUILD
+++ b/frc971/autonomous/BUILD
@@ -32,12 +32,14 @@
         ":auto_fbs",
         "//aos/actions:action_lib",
         "//aos/logging",
+        "//aos/util:math",
         "//aos/util:phased_loop",
         "//frc971/control_loops:control_loops_fbs",
         "//frc971/control_loops/drivetrain:drivetrain_config",
         "//frc971/control_loops/drivetrain:drivetrain_goal_fbs",
         "//frc971/control_loops/drivetrain:drivetrain_status_fbs",
         "//frc971/control_loops/drivetrain:localizer_fbs",
+        "//frc971/control_loops/drivetrain:spline",
         "//frc971/control_loops/drivetrain:spline_goal_fbs",
         "//y2019/control_loops/drivetrain:target_selector_fbs",
     ],