* example using the Canny algorithm with custom image gradient.

* Modified example to integrate new function canny with custom gradient

Also fixed some typos and code alignment
Also adapted tutorial CPP samples
Fixed some identation problems

This reverts commit 54a202b3.

Conflicts:
	modules/core/doc/command_line_parser.rst
	modules/core/include/opencv2/core/core.hpp
	modules/core/src/cmdparser.cpp
	modules/gpu/perf/main.cpp
	modules/gpu/test/main.cpp
	modules/ts/src/ts_perf.cpp