[openstack|network] create_network provider extensions

Implements provider extensions when creating networks.

See:

http://docs.openstack.org/trunk/openstack-network/admin/content/provider_attributes.html

Complements #1581 (Added missing Network model attributes)
[openstack|network] create_network provider extensions reworked

- Differenciate provider and vanilla options
- Fixed mocks
[openstack|network] remove extra trailing comma
[rackspace] adding auth 2.0 to compute, databases, dns, load balancers, cloud block storage
[rackspace|blockstorage] adding Cloud Block Storage Examples
Merge branch 'default_endpoint' of github.com:rackspace/fog into auth_deux
[rackspace|compute_v2] updated detach volume to use :rackspace_region to specify region
[rackspace] updated service endpoint handling; improved service endpoint tests
[rackspace] moving require 'fog/rackspace/service' to fog/rackspace
[rackspace] fixing auth 20 issue where tenant id is not being appended to the service url
Merge branch 'master' of github.com:fog/fog into auth_deux
Merge branch 'master' of github.com:fog/fog into auth_deux
rackspace|compute_v2] removing superfluous note from compute_v2 documentation
[rackspace|block_storage] initial document checkin.
[rackspace|block_storage] edits to cloud block storage documentation
[rackspace] adjusting white space on documents. Added examples, additional resources, and support section to cloud files doc.
Merge branch 'master' of github.com:fog/fog into auth_deux
[openstack|network] remove superfluous Router model attributes

See #1603
[aws] mock update_server_certificate
[rackspace] updated to normalize endpoints before detecting a standard endpoint.