Keep a count of the total number of balls shot

When a ball is in the flywheel, the friction causes
the flywheel velocity to slow down. It speeds up again when the
ball is shot. We can use this to determine when balls are shot.
For more details on this thought process, see
https://docs.google.com/document/d/1XHSnfcRiM3RihTK9LcC3zZn9kPMiARX02v4XhrQpidE/edit?usp=sharing

Change-Id: I2a0378c94cbc364f18c0af0df1706f046daf530b
Signed-off-by: milind-u <milind.upadhyay@gmail.com>
diff --git a/y2020/control_loops/superstructure/superstructure_status.fbs b/y2020/control_loops/superstructure/superstructure_status.fbs
index e55e19b..aab1341 100644
--- a/y2020/control_loops/superstructure/superstructure_status.fbs
+++ b/y2020/control_loops/superstructure/superstructure_status.fbs
@@ -37,6 +37,9 @@
   // If the shooter is ready, this is true.  Note: don't use this for status
   // checking, only for plotting.  Changes in goal take time to impact this.
   ready:bool (id: 3);
+
+  // The total number of balls we have shot
+  balls_shot:int (id: 4);
 }
 
 table AimerStatus {