Auto Exposure:

  - Filter results down to the three best.
  - Changing exposure based on distance to the target or at random.
  - Plumb exposure through the debug framework.
  - Refactor into target finder.

Change-Id: Ia083f56859938bf0825472fd15d248c545f6f2fc
diff --git a/aos/vision/debug/aveugle-source.cc b/aos/vision/debug/aveugle-source.cc
index cbe3d0a..d03be14 100644
--- a/aos/vision/debug/aveugle-source.cc
+++ b/aos/vision/debug/aveugle-source.cc
@@ -46,6 +46,9 @@
           ++i_;
         }
       });
+      interface_->InstallSetExposure([this](int abs_exp) {
+          this->SetExposure(abs_exp);
+      });
     }
     void ProcessImage(DataRef data, aos::monotonic_clock::time_point) override {
       prev_data_ = std::string(data);