Custom locale support

I added support for custom locales via ``` --locale``` in the command line or ``` locale:``` in the config file. The supported locales are in ``` /var/lib/locales/supported.d```.

Please check my changes carefully since this is the first time I've ever worked with Python. On my system it works at least.

One thing I can't check is the behaviour of locales with non-UTF-8 characters. I think there would be problems with the output.