Shain/client logger

:construction: Still some things not quite fleshed out, but a good starting place.

Basically, this proposes a new logging framework/style that retains backwards compatibility (if needed) and allows a simpler, more modular approach to creating and configuring loggers for the chef client. Also included would be some new loggers giving native support for syslog (finally!) and Windows (covered in a separate RFC)
We should get more crisp in here in terms of the functions one needs to implement and the options one needs to adhere (e.g. `log_level`) here if we want to enable custom loggers.