Tesseract coding style: Using clang-format and clang-tidy

[stweil]

From time to time Ray cleans the code by using clang-tidy. It would be nice to document that process to allow other developers to check their code contributions and avoid style problems from the beginning.

The current tidy process does not cover some significant code style issues. Most noticeable: it does not change from ( xxx ) (about 480 lines of code) to (xxx) (which is the preferred Google style, more than 50000 lines of code).

[egorpugin]

For code style clang-format could be applied.

[zdenop]

@stweil : anything else should be done here?

[stweil]

Pull request #1935 fixes style issues for some more code. I think for 4.0.0 this is sufficient.

[zdenop]

thanks.