Print out the diffs between ideal and solved

For each target in the target map, print the difference between
the solved map and the ideal (given target map), from the perpsective
of the ideal reference frame

Change-Id: I1469a39cf29558fc800f7a026865184ea70637c4
Signed-off-by: Jim Ostrowski <yimmy13@gmail.com>
diff --git a/frc971/vision/target_mapper.h b/frc971/vision/target_mapper.h
index a4c12b2..d1d122e 100644
--- a/frc971/vision/target_mapper.h
+++ b/frc971/vision/target_mapper.h
@@ -61,6 +61,7 @@
 
   void DumpConstraints(std::string_view path) const;
   void DumpStats(std::string_view path) const;
+  void PrintDiffs() const;
 
  private:
   // Error in an estimated pose