Add claw control loop.

It's based pretty heavily on the fridge loop. Currently, all the
tests pass.

Change-Id: Ieb386dfa5c3fe2d34e2d191fa39a44dc77ee6ab6
diff --git a/frc971/control_loops/fridge/fridge.cc b/frc971/control_loops/fridge/fridge.cc
index dae8374..b0ee642 100644
--- a/frc971/control_loops/fridge/fridge.cc
+++ b/frc971/control_loops/fridge/fridge.cc
@@ -15,8 +15,6 @@
 namespace frc971 {
 namespace control_loops {
 
-constexpr double Fridge::dt;
-
 namespace {
 constexpr double kZeroingVoltage = 4.0;
 constexpr double kElevatorZeroingVelocity = 0.10;
@@ -321,7 +319,8 @@
         LOG(DEBUG, "Zeroed the elevator!\n");
       } else if (!disable) {
         elevator_goal_velocity = elevator_zeroing_velocity();
-        elevator_goal_ += elevator_goal_velocity * dt;
+        elevator_goal_ += elevator_goal_velocity *
+            ::aos::controls::kLoopFrequency.ToSeconds();
       }
       break;
 
@@ -337,7 +336,8 @@
         LOG(DEBUG, "Zeroed the arm!\n");
       } else if (!disable) {
         arm_goal_velocity = arm_zeroing_velocity();
-        arm_goal_ += arm_goal_velocity * dt;
+        arm_goal_ += arm_goal_velocity *
+            ::aos::controls::kLoopFrequency.ToSeconds();
       }
       break;
 
diff --git a/frc971/control_loops/fridge/fridge.h b/frc971/control_loops/fridge/fridge.h
index 87dbfa4..54dc032 100644
--- a/frc971/control_loops/fridge/fridge.h
+++ b/frc971/control_loops/fridge/fridge.h
@@ -45,15 +45,6 @@
   explicit Fridge(
       control_loops::FridgeQueue *fridge_queue = &control_loops::fridge_queue);
 
-  // Control loop time step.
-  // Please figure out how to set dt from a common location
-  // Please decide the correct value
-  // Please use dt in your implementation so we can change looptimnig
-  // and be consistent with legacy
-  // And Brian please approve my code review as people are wait on
-  // these files to exist and they will be rewritten anyway
-  //static constexpr double dt;
-
   enum State {
     // Waiting to receive data before doing anything.
     UNINITIALIZED = 0,
@@ -148,7 +139,6 @@
   State last_state_ = UNINITIALIZED;
 
   control_loops::FridgeQueue::Position current_position_;
-  static constexpr double dt = 0.005;
 };
 
 }  // namespace control_loops