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)
	- test apps (namely ovs_vsctl.py and ovsdb_client.py) are left
	  intact.  they are now broken as i removed the evil "--" handing
	  in ryu-manager.

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

sync a sample confuguration and documentation with the code.

Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
fix a typo in simple_vlan _CONTEXTS

the _CONTEXTS mechanism seems prone to break.

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>
move openstack.common into the contrib directory

adjust import order in ryu-manager and add a comment.

Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
improve english in a comment

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