Added some useful debug utilities

debug_webcam_test.py: A basic tool to confirm your webcam works with
OpenCV.

debug_object_detection_test.py: Utility based on the complete
minnowboard_fish_picker-upper.py program, which only opens the webcam
feed and attempts object detection, without controlling the robot arm.
This can be useful when testing out haar paramters to account for
lighting conditions at your setup location.

Signed-off-by: Scott Garman <scott.a.garman@intel.com>
minnowboard_fish_picker-upper.py: various improvements

A significant refactoring of the program.

* Lowered CPU utilization by optmizing cv.WaitKey delay
* Trigger start of fish searching via a GPIO button press
* If a fish is not found, the arm will now rotate back and forth
  indefinitely until it finds one
* Clarified that image_scale is the main variable to tweak to account
  for lighting changes

Signed-off-by: Scott Garman <scott.a.garman@intel.com>
README: Updated documentation

GPIO switch wiring instructions to be available soon.

Signed-off-by: Scott Garman <scott.a.garman@intel.com>