Fixed RegEx for logout in 14w18b, first_login and last_login, using whitelist

Hi !

It's a big pull request, but here is my additions to your wonderful tool.

* Output now include First login and Last login dates
* REGEX_LOGOUT_USERNAME2 has been fixed (wasn't working with 14w18b)

Big new feature : 
* `-w whitelist.json` argument : you can now use the whitelist to filter the output
    * Users included on the whitelist but **not in the log** will be **included in the output, with zero values**
    * Users **not included in the whitelist** but included in the log will be **discarded before output rendering**

Please note that I'm not used to python, I think that's the second time I use this language, feel free to correct me on anything.

Thanks,
Pof.