Added warn to complement info, error.
Added info() and error() as aliases for lg.info() and lg.error()
First crack at restoring mininet python style, assisted by handy'unpep8' script, which does most of the work.
- topo.py is still in pep8- not all examples work, but this is due to other issues
Renamed logging_mod.py -> log.py
Updated other files accordingly.