Added cv2.boxPoints() functionality to Python bindings (Feature #2023)

http://www.code.opencv.org/issues/2023

eg:

In [3]: box = ((10,10),(5,5),0)

In [4]: cv2.boxPoints(box)
Out[4]:
array([[  7.5,  12.5],
       [  7.5,   7.5],
       [ 12.5,   7.5],
       [ 12.5,  12.5]], dtype=float32)

modules/imgproc/src/rotcalipers.cpp

@@ -398,3 +398,10 @@ cvMinAreaRect2( const CvArr* array, CvMemStorage* /*storage*/ )
     return (CvBox2D)rr;
 }
 
+void cv::boxPoints(cv::RotatedRect box, OutputArray _pts)
+{
+    _pts.create(4, 2, CV_32F);
+    Mat pts = _pts.getMat();
+    box.points((Point2f*)pts.data);
+}
+