Introducing easylogging++ as versatile logging framework

I've played around a little bit with [easylogging++](https://github.com/easylogging/easyloggingpp) and incorporated it with basic functionallity.
Mea culpa. I haven't thought about that parallel IO ... I'll rethink the stuff with the default configuration and look for a way to incorporate this into some header files to be tuned by the user at compile time.