Make entropy suitable for pypi distribution, part 2

Correct logging: reset loggers in engine.py, and setup your own
Added functions to setup logging in engine.py and Audit class,
can be used by audit scripts. Added a reset_logger function in utils

Expose __main__.py as a CLI on packaging. So after installing
the entropy package, you can call commands like
entropy register-audit
entropy start-engine
from anywhere in your machine. Made changes to setup.cfg to make
the main function an entry point.

Moved the engine_cfg file to /tmp/engines.cfg. That way, even though
it is hardcoded, it's at least fairly uniform across machines.

Change-Id: I704bf5e4635ffc539d7a73c5f84ef4bf8b2e801e