Fix bug in camera_calibration.cpp that the program tries to
parse input of type VIDEO_FILE as IMAGE_LIST which causes the
program to crash.

If-condition was always true (alpha = 0.5 is set in Line 19).
Now the user input is checked to be between 0 and 1.
This is correct in the tutorial code for OpenCV 2.4.

 - brush up the implementation

* fix typos.

* Fix typos.

* Fix typos.

* Fix typos.

* Fix typos.

Now a user can use `std::cout` to print an object of `cv::UMat` just like `cv::Mat`.

 - add more channels/depth performance test for blend

* Fix the documentation for Mat::diag(int).

Fix issue #8181

* Fix the documentation for Mat::diag(int).

Fix issue #8181.

* Add support for printing out cv::Complex.

* Remove extra spaces.

* cv::Complex is submitted as a new pull request.