Improve output verbosity and format, and tune Skill Level as an example

[ddugovic]

During initialization, print engine output including warnings/errors which may occur (such as "No such option: Aggressiveness")

Output shows interval using "x ± step" for readability

Since Stockfish no longer has an Aggressiveness parameter, change example to tune Skill Level

[ianfab]

At this point I should probably say that I did not know much more of Perl than its name when I forked the SPSA tuner and it has not changed much since then. I just added code using syntax I concluded from the context.

Anyway, the changes look fine to me as far as I can judge. Just a very minor point: I would prefer not to change the path of the executable in the example as this usually is the file name after having compiled Stockfish.

[ddugovic]

Thanks for pointing that out. I have changed back the engine name... oh, and the engine path which I had forgotten I changed.

[ddugovic]

I admit that over a decade ago I edited one or two Perl files and I too am learning Perl. I ran SPSA many times until I got a basic familiarity with it (and the "simulate" mode was very helpful in that discovery process).