Change initial verbosity of the logfile logger to DEBUG.

Otherwise, all debug messages created before proper file logging is set
up would be ignored.

Problem: You now ALWAYS get all debug messages, regardless of the
specified loglevel in the configuration file until changing to the
proper FileHandler, i.e. all debug messages of the configuration file
parser. Maybe there is some option to remove all messages below a certain level
before flushing the MemoryHandler into the FileHandler? But good for now, as
debug output in the logfile is desired behaviour.