docs: Update commiter guide.
Add ex_create_subscription method to CloudSigma driver. Also modify
subscription class so the amount attribute is an int.
Add auto_renew attribute to subscription class.
Include subscribed_object attribute on the Subscription class.
Allow user to create server with VLAN.
docs: Add an example of how to create a server with a vlan.
Add a test case for creating a node with VLAN.
Fix documentation build issue.
Use virtio device type.
ex_list_drives -> ex_list_user_drives.
Add ex_list_library_drives method.
If user specifies an installation CD image, use ide instead of virtio device
type.
docs: Add an example which shows how to create a server using an installation
cd.
Use a separate method to detect an installation cd.
No need to clone installation CDs, update docstring.
docs: Add example.
Add test for ex_list_library_drives method.
docs: Add image to the provider docs.
docs: Add information about library drives and server creation work flow.
Add an example of how to purchase a subscription.