Add new field 'refresh_on' to task.yaml

Task.yaml should have new field named 'refresh_on', field should contain list
of puppet resources names (keystone_config, nova_config, ...).

If user upload YAML with 'keystone_config' all granular with refresh_on ['keystone_config'] should be executed.

'refresh_on' can handle multiple resources, ex. refresh on 'keystone_config' AND 'nova_config' change.

If 'refresh_on' is empty, or missing - it should not be executed never after configuration manipulation.