Tune flywheels

Switch to hybrid kalman filter, plot voltage error

Change-Id: I9ade9a741aae58bdb3818c23bfe91b18786235f3
diff --git a/y2020/control_loops/superstructure/superstructure_status.fbs b/y2020/control_loops/superstructure/superstructure_status.fbs
index e8f7637..0b12d33 100644
--- a/y2020/control_loops/superstructure/superstructure_status.fbs
+++ b/y2020/control_loops/superstructure/superstructure_status.fbs
@@ -14,6 +14,9 @@
   // The target speed selected by the lookup table or from manual override
   // Can be compared to velocity to determine if ready.
   angular_velocity_goal:double;
+
+  // Voltage error.
+  voltage_error:double;
 }
 
 table ShooterStatus {