Cinder changes to support create volume types in quickstack

Add the cinder_create_volume_types param and default to true
Change the cinder backend type strings to shorter strings (without
_backend)
simple subnets
Simple Subnets UI
Simple Subnets validations
Simple Subnets: fix network_address validation
Simple Subnets: UI fixes

- Makes the "New Subnet" button green
- Adds inline help for "Network Address"
- Sets "External DHCP" as the default value for dhpc_server
Merge pull request #338 from ares/simple_subnets_backend

Simple subnets backend
Simple Subnets: update the network_configuration page

Append the newly created subnet to the list of subnets.
Merge pull request #339 from ifarkas/simple_subnet-auto_refresh

Simple Subnets: update the network_configuration page
Merge pull request #331 from bcrochet/new-cinder-names

Cinder changes to support create volume types in quickstack