Fix logging in brain.py

Fixed logging in brain.py.

Formatting, (File-)handling, etc. should be defined globally in `jasper.py` and not per module (not to mention per logging call). Please see ["Good logging practice in Python"](http://victorlin.me/posts/2012/08/26/good-logging-practice-in-python) for details.

Besides: Writing logfiles without the users permission should not happen, because they consume flash write cycles and therefore may break the SD card.