Add JsonFormat to handle json logs without regex parsing. #120

Used to live import nginx logs to piwik.

Thank you for the PR!

Here is code review (these items will help us merge in core)

• can you add example log file in JSON format in: https://github.com/piwik/piwik/tree/master/misc/log-analytics/tests/logs and update test script https://github.com/piwik/piwik/blob/master/misc/log-analytics/tests/tests.py
• in the markdown update # Setup Nginx logs should be ### Setup Nginx logs
• Also move this new README update to the very bottom of the README file
• in the new code why do you have to catch this new exception KeyError? (Im not familiar with Python)

Cheers

OK I will do that.

For the Exception, it's due to the method to parse lines: one use regex which throw IndexError exception, mine use a hash which throw KeyError. I think the best method should be to throw a specific exception, say "NotFound", for both and futur classes.

Thanks for the PR! Really useful :+1:

indeed nice work!