Simplify logging

[jnehring]

Right now there are plenty of logfiles. Two logfiles in the "log" folder, one log file per experiment (57 in the current installation) and one per task (I estimate 200 logfiles). Evaluating 260 different logfiles is a challenging and time consuming tasks.

I suggest to

• Use a logging library, e.g. Monolog instead of the homemade logger
• Configure the logging in a way that it creates a single logfile instead of 260 different log files.

This might not be a cool new feature for showing off but I think it will speed up all future development and administrative tasks. And there are two indicators that this is easy to implement: The currently used homemade logger implements the Logger interface. And the system uses a dependency injection framework.

Using a logging library we might solve #38 with a few lines of configuration.