Add methods to create and delete networks
Add methods to create and delete networks

The create_network() method currently does not support admin-level
operations. This will be added real soon now.

Change-Id: I5909b3cafd9c418f953a76cfaaf5c5708ad7e945

jsmartin/shade,dtroyer/python-openstacksdk,openstack/python-openstacksdk,openstack/python-openstacksdk,stackforge/python-openstacksdk,jsmartin/shade,openstack-infra/shade,openstack-infra/shade,stackforge/python-openstacksdk,dtroyer/python-openstacksdk