Update network related extension methods so they work correctly with
both, OpenStack and Rackspace driver.

Part of LIBCLOUD-368.
Add tests for OpenStack and Rackspace networks functionality.
docs: Add more OpenStack driver docs.
docs: Link to the provider documentation page from the provider matrix table.
docs: Display providers in the supported providers and supported methods table
in an alphabetical order.
Issue LIBCLOUD-408: Pass kwargs to ex_rebuild to create node args

Added test that verifies this does the expected thing for the
disk configuration option.

Signed-off-by: Tomaz Muraus <tomaz@apache.org>
Remove unnecessary try / except blocks.
Update changes.
Add test for auth url being set on the Rackspace First gen driver.
Update Rackspace compute drivers to correctly handle "region" argument.
Add tests for "region" argument in the Rackspace compute drivers.
Less copy and pasting in Rackspace test cases.
Add pricing information for Rackspace cloud Sydney region.
Assign region instance variable in the BaseDriver class.
pep8 fixes in test_rackspace.py.
pep8 fixes in libcloud.common.openstack.py.
Update CHANGES.
Update region handling in the CloudFiles driver.