Rename API payload properties names to resource_config.

[EarthmanT]

For example:

  cloudify.openstack.nodes.Server:
    derived_from: cloudify.nodes.Compute
    properties:
      server:
        default: {}
        description: >
          The keypair object as described in OpenStack compute API (create server method):
          https://developer.openstack.org/api-ref/compute/#servers-servers

Should be changed to:

  cloudify.openstack.nodes.Server:
    derived_from: cloudify.nodes.Compute
    properties:
      resource_config:
        default: {}
        description: >
          The keypair object as described in OpenStack compute API (create server method):
          https://developer.openstack.org/api-ref/compute/#servers-servers