Added position control and profiling to drivetrain.

Change-Id: I09ad01c46b23f1c7b6e8530bc10b03a733245b95
diff --git a/frc971/control_loops/state_feedback_loop.h b/frc971/control_loops/state_feedback_loop.h
index a51564b..e78a786 100644
--- a/frc971/control_loops/state_feedback_loop.h
+++ b/frc971/control_loops/state_feedback_loop.h
@@ -416,6 +416,12 @@
     }
 
     UpdateObserver(U_);
+
+    UpdateFFReference();
+  }
+
+  // Updates R() after any CapU operations happen on U().
+  void UpdateFFReference() {
     ff_U_ -= U_uncapped() - U();
     if (!Kff().isZero(0)) {
       R_ = A() * R() + B() * ff_U_;