Renamed ZeroingEstimator to PotAndIndexPulseZeroingEstimator

Renamed to allow for creating a new interface named ZeroingEstimator
in the future.

Change-Id: I374808cdc39dd4141ea67c81de69bbac98326648
diff --git a/y2014/constants.h b/y2014/constants.h
index 4ad06bc..7fb2507 100644
--- a/y2014/constants.h
+++ b/y2014/constants.h
@@ -43,7 +43,7 @@
 
   double drivetrain_max_speed;
 
-  struct ZeroingConstants {
+  struct PotAndIndexPulseZeroingConstants {
     // The number of samples in the moving average filter.
     int average_filter_size;
     // The difference in scaled units between two index pulses.
@@ -126,7 +126,7 @@
     // should be larger than claw_shooting_separation so that we can shoot
     // promptly.
     double claw_separation_goal;
-   };
+  };
   ShooterAction shooter_action;
 };