Solve performance issue

[cghielmini]

This PR addresses all improvements mentioned in issue #91 :

• Clearer CLI/config naming (timing_regex renamed in log_file).
• Time regex is now more robust.
• CLI help description for timing_database is accurate and informative.

[huppd]

Thanks, this is a greate improvement, it makes using it much clearer and makes it more robust. I commited some changes in the test to be sure that now the tool covers more date formats. I only have some minor suggestions.

[cghielmini]

Thanks for your comments, I added your suggestions.

[huppd]

Perfect, thanks a lot!

[cghielmini]

is it better now?

[huppd]

Yes, it is better now. Thanks :)