import cfg.py from oslo-incubator

import cfg.py taken from:
	https://github.com/openstack/oslo-incubator.git
	commit 30a50c8a6c534f01d518eb3ce4cf0d35877d9a7f

we are going to switch from python-gflags to openstack cfg.py
because the latter is more flexible wrt schema modifications.
eg. it allows introducing options at module import time.

references:
	http://wiki.openstack.org/CommonConfigModule

Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
use openstack.common.cfg instead of gflags

make most of modules use openstack.common.cfg instead of gflags

caveats: no config file compatibility is provided.  (flagfile vs ini file)

Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
adjust import order in ryu-manager and add a comment.

Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
update a sample and documentation

try to sync the documentation with the reality at least about
gflags/cfg changes.

Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
fix a typo in the help message of quantum_controller_addr

Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
stop requiring gflags

Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>