Renamed ZeroingEstimator to PotAndIndexPulseZeroingEstimator

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

Change-Id: I374808cdc39dd4141ea67c81de69bbac98326648
diff --git a/frc971/constants.h b/frc971/constants.h
index 0da9c96..fbf7b1c 100644
--- a/frc971/constants.h
+++ b/frc971/constants.h
@@ -4,7 +4,7 @@
 namespace frc971 {
 namespace constants {
 
-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.