Added a start at a fridge.

Change-Id: I5bab9686f966368161ede528ff7abf038d7bcb9a
diff --git a/frc971/constants.h b/frc971/constants.h
index 4a793ae..eca49d7 100644
--- a/frc971/constants.h
+++ b/frc971/constants.h
@@ -37,10 +37,12 @@
   // Superstructure Values /////
 
   struct ZeroingConstants {
+    // The number of samples in the moving average filter.
     int average_filter_size;
+    // The difference in SI units between two index pulses.
     double index_difference;
-    // Offset between the physical encoder index and the index we want.
-    double index_offset_at_zero;
+    // The absolute position in SI units of one of the index pulses.
+    double measured_index_position;
   };
 
   ZeroingConstants left_arm_zeroing_constants;
@@ -67,6 +69,9 @@
     Range arm;
   };
   Fridge fridge;
+
+  double max_allowed_left_right_arm_difference;
+  double max_allowed_left_right_elevator_difference;
 };
 
 // Creates (once) a Values instance for ::aos::network::GetTeamNumber() and