Add ability to use systemd journald, rather than log file

I was interested in having fail2ban working with systemd's journald. I've added code to allow fail2ban to read from journald and also allow to set match filters as per journalctl. As far as I can tell, all/most the regex filters still work.

It required use of a python interface to journald, which I couldn't find anywhere, so I've knocked one up myself. It's python c-api wrap around the systemd journal C API, sd-journal. Code for this is on my github https://github.com/kwirk/pyjournalctl

Initial testing shows all working okay, but if anyone else could do some testing, that would be great.

Any feedback appreciated.