Remove useless backslash.

1. Explain grayscale input still read as three channel
2. Fix typo
3. Add more details to image match explanation to include the use of masks

There were two bugs that were solved here.Changes were done after extreme testing.
1.replaced cv2.solvePnPRansac() with cv2.solvePnP() previous fc was giving terrible errors.
2.The code was incapable of saving edited pics;Now fixed with little code mods.

In the camera calibration code { cv2.cornerSubPix() } will be of no use.In the updated code it is assigned to the (corners2) variable 
which is passed down to { cv2.drawChessboardCorners() }

Save method should save, instead trying to run inkview

- added HAL documentation support
- added documentation to HAL replacement interface
- updated several HAL functions in imgproc module

Extension of the camera distortion model for tilted image sensors (Scheimpflug condition) including test

Add py_hdr tutorial under py_tutorials\py_photo.
This tutorial is similar to the one which is given at the C++ tutorials.

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