reg: add python sample

modules/reg/samples/reg_shift.py

+#!/usr/bin/python
+
+import cv2
+import numpy as np
+import sys
+
+img1 = cv2.imread(sys.argv[1])
+img1 = img1.astype(np.float32)
+shift = np.array([5., 5.])
+mapTest = cv2.reg.MapShift(shift)
+
+img2 = mapTest.warp(img1)
+
+mapper = cv2.reg.MapperGradShift()
+mappPyr = cv2.reg.MapperPyramid(mapper)
+
+resMap = mappPyr.calculate(img1, img2)
+mapShift = cv2.reg.MapTypeCaster_toShift(resMap)
+
+print(mapShift.getShift())