Add static code checking for style and errors

This required a change to logging, which now uses a singleton pattern.

For all future checkins, 'make codecheck' should pass.

Makefile

@@ -1,5 +1,12 @@
+all: codecheck test
+
 clean:
 	rm -rf build dist build *.egg-info *.pyc
 
+codecheck: mininet/*.py mininet/test/*.py
+	pyflakes mininet/*.py mininet/test/*.py bin/*.py
+	pylint --rcfile=.pylint mininet/*.py mininet/test/*.py bin/*.py
+	pep8 --ignore=E251 mininet/*.py mininet/test/*.py bin/*.py
+
 test: mininet/*.py mininet/test/*.py
-	mininet/test/test_nets.py
+	mininet/test/test_nets.py