* Check application description version during validation.
* Bump application description version to 2 since we are going to make some major changes in the format
* Add fields `total_count`, `essential_count` and `startup_order` to service descriptions.
* Comment code related to the parsing of cluster statistics from Swarm. The data returned by API changes too often and parsing it consistently is too complex. A bug is open on the Swarm issue tracker.