work on obj_detect.py

added square_size cmd line param for calibrate.py
added _coverage.py script to compute cv2 api coverage by samples (just for interest, may be removed later)

samples/python2/_coverage.py

@@ -0,0 +1,21 @@
+from glob import glob
+import cv2
+import re
+
+cv2_callable = set(['cv2.'+name for name in dir(cv2) if callable( getattr(cv2, name) )])
+
+found = set()
+for fn in glob('*.py'):
+    print ' --- ', fn
+    code = open(fn).read()
+    found |= set(re.findall('cv2?\.\w+', code))
+
+cv2_used = found & cv2_callable
+
+r = 1.0 * len(cv2_used) / len(cv2_callable)
+print '\ncv2 api coverage: %d / %d  (%.1f%%)' % ( len(cv2_used), len(cv2_callable), r*100 )
+
+print '\nold (cv) symbols:'
+for s in found:
+    if s.startswith('cv.'):
+        print s