Adding target point definition and calculation (x,y,radius) for visualization

Apologies in advance for:
1) Changing flatbuffer definitions
1a) Moved to camera poses, since I think it really belongs there
1b) Changed name of target, since it had same name as those in trainging data
2) A lot of formatting from running yapf, buildifier, clang-format.
(BUILD, target_definition_test.py have formatting changes only)
(define_training_data.py and load_sift_training.py are mostly formatting)

Change-Id: Iace1261ea5f04aeb8103b5b9a9d6da5ec3328293
diff --git a/y2020/vision/sift/sift_training.fbs b/y2020/vision/sift/sift_training.fbs
index d4fa740..12ad9b4 100644
--- a/y2020/vision/sift/sift_training.fbs
+++ b/y2020/vision/sift/sift_training.fbs
@@ -14,6 +14,8 @@
   // 2D image coordinate representing target location on the training image
   target_point_x:float;
   target_point_y:float;
+  // Radius of target circle
+  target_point_radius:float;
 }
 
 // Represents the information used to match incoming images against.