Display has_piece on the webpage

Change-Id: I81ff1c7a821e55c35207613f0045582f5ecb6175
diff --git a/y2019/vision/server/server_data.proto b/y2019/vision/server/server_data.proto
index 96a5859..1fe8ec2 100644
--- a/y2019/vision/server/server_data.proto
+++ b/y2019/vision/server/server_data.proto
@@ -47,6 +47,7 @@
   optional float elevator = 2;
   optional float intake = 3;
   optional float stilts = 4;
+  optional bool has_piece = 5;
 }
 
 // The overall package of data that we send to the webpage.