adding missing images from python tutorials, like chessboard.png, simple.jpg, home.jpg, fly.png, ...

doc/py_tutorials/py_feature2d/py_features_harris/py_features_harris.markdown

@@ -77,7 +77,7 @@ See the example below:
 import cv2
 import numpy as np
 
-filename = 'chessboard.jpg'
+filename = 'chessboard.png'
 img = cv2.imread(filename)
 gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)
 

doc/py_tutorials/py_feature2d/py_shi_tomasi/py_shi_tomasi.markdown

@@ -50,7 +50,7 @@ import numpy as np
 import cv2
 from matplotlib import pyplot as plt
 
-img = cv2.imread('simple.jpg')
+img = cv2.imread('blox.jpg')
 gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)
 
 corners = cv2.goodFeaturesToTrack(gray,25,0.01,10)