Change HallEffectAndPosition to proper naming

All of the templates assume the position variable is called encoder,
not position. I spent a while trying to figure out if the naming
should be the other way around, but I think 'encoder' is correct.

Change-Id: Icb0fa9a94bdea4ae3a43b947a073cc1f83ba5f4a
diff --git a/y2017/control_loops/superstructure/column/column.cc b/y2017/control_loops/superstructure/column/column.cc
index aaca601..8a3644e 100644
--- a/y2017/control_loops/superstructure/column/column.cc
+++ b/y2017/control_loops/superstructure/column/column.cc
@@ -118,19 +118,19 @@
   }
 
   turret_last_position_ = turret_position();
-  Y_ << new_position.indexer.position, new_position.turret.position;
+  Y_ << new_position.indexer.encoder, new_position.turret.encoder;
   Y_ += offset_;
   loop_->Correct(Y_);
 
-  indexer_history_[indexer_history_position_] = new_position.indexer.position;
+  indexer_history_[indexer_history_position_] = new_position.indexer.encoder;
   indexer_history_position_ = (indexer_history_position_ + 1) % kHistoryLength;
 
   indexer_dt_velocity_ =
-      (new_position.indexer.position - indexer_last_position_) /
+      (new_position.indexer.encoder - indexer_last_position_) /
       chrono::duration_cast<chrono::duration<double>>(
           ::aos::controls::kLoopFrequency)
           .count();
-  indexer_last_position_ = new_position.indexer.position;
+  indexer_last_position_ = new_position.indexer.encoder;
 
   stuck_indexer_detector_->Correct(Y_);
 
diff --git a/y2017/control_loops/superstructure/column/column_zeroing.cc b/y2017/control_loops/superstructure/column/column_zeroing.cc
index e26d33e..d5a378c 100644
--- a/y2017/control_loops/superstructure/column/column_zeroing.cc
+++ b/y2017/control_loops/superstructure/column/column_zeroing.cc
@@ -38,8 +38,8 @@
     indexer_offset_ = indexer_.offset();
 
     // Compute the current turret position.
-    const double current_turret = indexer_offset_ + position.indexer.position +
-                                  turret_.offset() + position.turret.position;
+    const double current_turret = indexer_offset_ + position.indexer.encoder +
+                                  turret_.offset() + position.turret.encoder;
 
     // Now, we can compute the turret position which is closest to 0 radians
     // (within +- M_PI).
@@ -47,14 +47,14 @@
         ::frc971::zeroing::Wrap(0.0, current_turret, M_PI * 2.0);
 
     // Now, compute the actual turret offset.
-    turret_offset_ = adjusted_turret - position.turret.position -
-                     (indexer_offset_ + position.indexer.position);
+    turret_offset_ = adjusted_turret - position.turret.encoder -
+                     (indexer_offset_ + position.indexer.encoder);
     offset_ready_ = true;
 
     // If we are close enough to 0, we are zeroed.  Otherwise, we don't know
     // which revolution we are on and need more info.  We will always report the
     // turret position as within +- M_PI from 0 with the provided offset.
-    if (::std::abs(position.indexer.position + position.turret.position +
+    if (::std::abs(position.indexer.encoder + position.turret.encoder +
                    indexer_offset_ + turret_offset_) <
         turret_zeroed_distance_) {
       zeroed_ = true;
diff --git a/y2017/control_loops/superstructure/superstructure_lib_test.cc b/y2017/control_loops/superstructure/superstructure_lib_test.cc
index d538dc8..894f99d 100644
--- a/y2017/control_loops/superstructure/superstructure_lib_test.cc
+++ b/y2017/control_loops/superstructure/superstructure_lib_test.cc
@@ -1066,7 +1066,7 @@
   superstructure_queue_.position.FetchLatest();
   ASSERT_TRUE(superstructure_queue_.position.get() != nullptr);
   const double indexer_position =
-      superstructure_queue_.position->column.indexer.position;
+      superstructure_queue_.position->column.indexer.encoder;
 
   // Now, unstick it.
   superstructure_plant_.set_freeze_indexer(false);
@@ -1094,7 +1094,7 @@
   superstructure_queue_.position.FetchLatest();
   ASSERT_TRUE(superstructure_queue_.position.get() != nullptr);
   const double unstuck_indexer_position =
-      superstructure_queue_.position->column.indexer.position;
+      superstructure_queue_.position->column.indexer.encoder;
   EXPECT_LT(unstuck_indexer_position, indexer_position - 0.1);
 
   // Now, verify that everything works as expected.
diff --git a/y2017/wpilib_interface.cc b/y2017/wpilib_interface.cc
index 01184fa..12f3313 100644
--- a/y2017/wpilib_interface.cc
+++ b/y2017/wpilib_interface.cc
@@ -453,7 +453,7 @@
                     double encoder_counts_per_revolution, double encoder_ratio,
                     bool reverse) {
     const double multiplier = reverse ? -1.0 : 1.0;
-    position->position =
+    position->encoder =
         multiplier * encoder_translate(counter.polled_encoder(),
                                        encoder_counts_per_revolution,
                                        encoder_ratio);