A cloud-config resource based on SoftwareConfig

This simple resource allows cloud-config to be specified
as a map property, and stores the resulting YAML as a SoftwareConfig
resource.

Because cloud-init is boot only, this resource won't be used with
a SoftwareDeployment resource, also it will not have inputs or outputs.

Instead, a server's user_data can contain this resource via get_resource
when user_data_format is SOFTWARE_CONFIG.

Implements: blueprint cloud-init-resource

Change-Id: I15c8d6a03b8da274531b76cca658e37def4eb460
Merge "A cloud-config resource based on SoftwareConfig"